Electro-optical device

ABSTRACT

In an active matrix semiconductor display device in which pixel TFTs and driver circuit TFT are formed on the same substrate in an integral manner, the cell gap is controlled by gap retaining members that are disposed between a pixel area and driver circuit areas. This makes it possible to provide a uniform cell thickness profile over the entire semiconductor display device. Further, since conventional grainy spacers are not used, stress is not imposed on the driver circuit TFTs when a TFT substrate and an opposed substrate are bonded together. This prevents the driver circuit TFTs from being damaged.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor display deviceusing thin-film transistors. In particular, the invention relates to asemiconductor display device in which a pixel switching circuit anddriver circuits are formed on the same substrate in an integral manner.

[0003] 2. Description of the Related Art

[0004] In recent years, the techniques of forming semiconductor devices,such as thin-film transistors (TFTs), by using a semiconductor thin filmformed on an inexpensive glass substrate have made rapid progress. Thisis because of increased demand for active matrix liquid crystal displaydevices.

[0005] In active matrix liquid crystal display devices, TFTs areprovided for respective ones of hundreds of thousands to millions ofpixel regions that are arranged in matrix and charge that enters orexits from each pixel electrode is controlled by the switching functionof the associated TFT.

[0006] The basic configuration of an active matrix liquid crystaldisplay device in which thin-film transistors are arranged will bedescribed below with reference to FIGS. 34A and 34B. FIG. 34A is asectional view obtained by cutting a liquid crystal display device by aplane perpendicular to a substrate, specifically taken along a chainline A-A′ in FIG. 34B.

[0007] An insulating film (not shown) is formed on the surface of atransparent base substrate 1. Reference numeral 2 denotes an activelayer of a TFT; 3, a gate electrode; 4, a data line; 5, a drainelectrode; 6, an interlayer insulating film; 7, a black matrix; 8, atransparent conductive film as a pixel electrode; and 9, an alignmentfilm.

[0008] In this specification, the structure including the base substrate1 and the other members mentioned above (including the TFTs) is calledan “TFT substrate.” Although FIG. 34A focuses on a single pixel,actually the TFT substrate is composed of a pixel area includinghundreds of thousands to millions of pixel switching TFTs (called pixelTFTs) and peripheral driver circuit areas including a number of TFTs fordriving the pixel TFTS.

[0009] On the other hand, reference numerals 10-12 denote a transparentsubstrate, a transparent conductive film as an opposed electrode, and analignment film, respectively. The structure including these members,which is opposed to the TFT substrate, is called an “opposed substrate.”

[0010] As shown in FIG. 35A, the TFT substrate 20 and the opposedsubstrate 30 are subjected to an alignment treatment such as rubbing forgiving proper alignment to a liquid crystal. Thereafter, to control asubstrate interval (cell gap) between the TFT substrate 20 and theopposed substrate 30, grainy spacers 41 are uniformly scattered over theentire surface of the TFT substrate 20. Then, a sealing agent 42 isprinted. The sealing agent 42 has a role of an adhesive for bonding thesubstrates 20 and 30 together as well as a role of a sealing materialfor sealing the space between the substrates 20 and 30 to prevent aliquid crystal material that will be injected there from leaking to theoutside of the substrates.

[0011]FIG. 36 is a sectional view of the TFT substrate 20. Since thegrainy spacers 41 are uniformly scattered over the entire surface of theTFT substrate 20 to control the cell gap, the spacers 41 exist in notonly the pixel area 22 but also the peripheral driver circuit regions 23as shown in FIG. 36. Usually, the pixel TFTs formed in the pixel area 22are not much different in device size from the driver circuit TFTsformed in the driver circuit areas 23. However, the black matrix forcovering the pixel TFTs, the pixel electrodes that are transparentconductive films, and other members are formed in the pixel area 22.Further, in reflection-type liquid crystal display devices, a reflectiveelectrode is formed in the pixel area 22. On the other hand, connectionlines necessary to constitute CMOS circuits for driving the pixel TFTsare formed in the driver circuit areas 23. Therefore, there aredifferences in the height (distance) from the surface of the basesubstrate 1 between the pixel area 22 and the driver circuit areas 23.

[0012] A description will now be made of a case where the height asmeasured from the surface of the substrate 1 in the pixel area 11 isgreater than in the driver circuit areas 23. The grainy spacers 41 arescattered in not only the pixel area 22 but also the driver circuitareas 23 by a wet or dry method. If the grainy spacers 41 haveapproximately uniform sizes, they have differences in the height asmeasured from the substrate 1 depending on their positions. Now, theheight of the top of each spacer 41 in the pixel area 22 and that of thetop of each spacer 41 in the driver circuit areas 23 are represented byhp and hd, respectively As seen from FIG. 36, a height differenceΔh=hp—hd occurs due to the difference in height between the pixel area22 and the driver circuit areas 23.

[0013] Then, as shown in FIG. 37A, the TFT substrate 20 and the opposedsubstrate 30 are bonded together with the sealing agent 42. Thereafter,the space between the TFT substrate 20 and the opposed substrate 30 arefilled with a liquid crystal material 43 and a liquid crystal injectioninlet 44 is sealed with a sealing material (see FIG. 37B). In thismanner, an active matrix liquid crystal display device having theconfiguration shown in FIG. 34A is obtained.

[0014] However, the liquid crystal display device having the aboveconfiguration has the following problems.

[0015] Because of the height difference ah that is caused by thedifference in height between the pixel area 22 and the driver circuitareas 23, the cell gas cannot be made uniform, that is, a cell thicknessvariation occurs, when the TFT substrate 20 and the opposed substrate 30are bonded together. Further, as shown in FIGS. 37A and 37B, strainoccurs in the opposed substrate 30. Defects such as display unevennessand an interference fringe (on the top surface of the opposed substrate)may occur in a liquid crystal display device having a cell thicknessvariation and strain in the opposed substrate 30.

[0016] Where the height as measured from the substrate 1 in the drivercircuit areas 23 is greater than in the pixel area 22, because of theabove-described height difference Ah, unduly strong force is exerted onthe spacers 41 that are scattered in the driver circuit areas 23 whenthe TFT substrate 20 and the opposed substrate 30 are bonded together.As a result, the driver circuit TFTs having a more complex structurethan the pixel TFTs are damaged considerably, which adversely affectsthe yield of products.

[0017] Where grainy spacers 15 exist in the pixel area, disorder inimage display (disclination) may be observed as shown in FIG. 34Bbecause the alignment of the liquid crystal material is disordered inthe vicinity of the spacers 15.

[0018] As described above, where the cell gap is controlled by usingconventional grainy spacers, satisfactory display may not be obtaineddue to various factors.

[0019] In liquid crystal display devices that are commonly manufacturedor manufactured as trial products, the cell gap appears to be set at 4-6μm irrespective of the pixel pitch. However, in the future, liquidcrystal panels will be required to have higher resolution and hence thepixel pitch will be increasingly reduced.

[0020] For example, projection-type liquid crystal display devices aredesired to be able to display images having as high resolution aspossible in view of the fact that the images are projected onto a screenin an enlarged manner. Also from the viewpoint of the cost, the opticalsystem needs to be miniaturized and the panel size needs to be reduced.For the above reasons, in the future, it will be necessary tomanufacture liquid crystal display devices having a pixel pitch of 40 μmor less, preferably 30 μm or less.

[0021] In liquid crystal display devices for displaying such highresolution images, even grainy spacers of several micrometers indiameter may deteriorate display quality when they exist in theeffective display area.

[0022] Further, when a liquid crystal material is injected, the flow ofthe liquid crystal material forces conventional grainy spacersthemselves to flow. As a result, a uniform spacer dispersion densityprofile may not be obtained, to cause a cell thickness variation.

[0023] Because of their characteristics, liquid crystal display devicesusing a ferroelectric liquid crystal that attract much attentionrecently and reflection-type liquid crystal display devices are requiredto have small cell gaps.

[0024] However, with conventional grainy spacers, it is generallydifficult to produce a cell having a small, uniform-profile cell gap.

SUMMARY OF THE INVENTION

[0025] An object of the present invention is to provide a semiconductordisplay device that is free of a cell thickness variation and displayunevenness by producing a cell having a small, uniform-profile cell gapthat is hard to realize with conventional grainy spacers.

[0026] Another object of the invention is to prevent TFTs from beingdamaged by preventing unnecessary stress that would otherwise be exertedon the TFTs in bonding substrates together when conventional grainyspacers are used.

[0027] According to one aspect of the invention, there is provided anelectro-optical device comprising a first substrate comprising a pixelarea having a plurality of thin-film transistors and a plurality ofpixel electrodes electrically connected to the respective thin-filmtransistors; a driver circuit area provided at a location separate fromthe pixel area and having a plurality of driver circuits having aplurality of thin-film transistors for driving the thin-film transistorsin the pixel area; and a base substrate; a second substrate thatconfronts the first substrate; a plurality of gap retaining members; anda sealing member for bonding the first and second substrates together,wherein a distance from a surface of the base substrate to a surface ofthe pixel area is different from a distance from the surface of the basesubstrate to a surface of the driver circuit area and wherein the gapretaining members are formed in an area other than the pixel area andthe driver circuit area. The above objects can be attained by thiselectro-optical device.

[0028] According to another aspect of the invention, there is providedan electro-optical device comprising a TFT substrate comprising a pixelarea having a plurality of pixel electrodes arranged in matrix form anda plurality of pixel thin-film transistors electrically connected to therespective pixel electrodes; a driver circuit area having a drivercircuit having a plurality of thin-film transistors for driving thepixel thin-film transistors; and a base substrate; an opposed substratethat confronts the TFT substrate; a display medium held between the TFTsubstrate and the opposed substrate, an optical response of the displaymedium being controlled by an application voltage; and a plurality ofgap retaining members, wherein a distance from a surface of the basesubstrate to a surface of the pixel area is different from a distancefrom the surface of the base substrate to a surface of the drivercircuit area and wherein the gap retaining members are formed in an areaother than the pixel area and the driver circuit area. The above objectscan be attained by this electro-optical device.

[0029] The above-mentioned optical medium may be such that its opticalcharacteristic is modulated in accordance with the application voltage.

[0030] The above-mentioned display medium may be a liquid crystal.

[0031] The above-mentioned display medium may be a mixed layer of aliquid crystal material and a polymer.

[0032] The above-mentioned display medium may be an electroluminescenceelement.

[0033] The above-mentioned gap retaining members may be formed aroundthe pixel area.

[0034] The arrangement density of the above-mentioned gap retainingmembers may be uniform in the pixel area.

[0035] Each of the above-mentioned gap retaining members may be shapedlike a cylinder.

[0036] Each of the above-mentioned gap retaining members may be shapedlike an elliptical pole.

[0037] Each of the above-mentioned gap retaining members may be shapedlike a polygonal prism.

[0038] Each of the above-mentioned gap retaining members may be shapedso as not to obstruct a flow of the liquid crystal when it is injected.

[0039] The side face of each of the above-mentioned gap retainingmembers may be tapered.

[0040] The above-mentioned gap retaining members may be made of onematerial selected from the group consisting of polyimide, acrylic,polyamide, and polyimideamide.

[0041] The above-mentioned gap retaining members may be made of anultraviolet curable resin.

[0042] The above-mentioned gap retaining members may be made of an epoxyresin.

[0043] According to another aspect of the invention, the top surfaces ofthe respective gap retaining members on the side of one of the first andsecond substrates have been planarized by chemical mechanical polishing.In this electro-optical device, since the cell gap is controlled byplanarizing the top surfaces of the gap retaining members, a small cellthickness having a uniform profile over the entire electro-opticaldevice can be obtained. Even if the gap retaining members are formed onthe pixel area or the driver circuits, a uniform cell thickness profilecan be obtained.

[0044] To attain the above objects, according to another aspect of theinvention, there is provided an electro-optical device comprising afirst substrate comprising a pixel area having a plurality of pixelelectrodes and switching elements connected to the respective pixelelectrodes; a second substrate confronting the first substrate; and agap retaining member that is provided on the second substrate andretains an interval between the first and second substrates.

[0045] To attain the above objects, according to a further aspect of theinvention, there is provided an electro-optical device comprising afirst substrate comprising a pixel area having a plurality of pixelelectrodes and switching elements connected to the respective pixelelectrodes; a second substrate confronting the first substrate; a liquidcrystal sealed in a space between the first and second substrates; afirst alignment film that is formed on a surface of the first substrateand orients a liquid crystal; a second alignment film that is formed onthe second substrate and orients the liquid crystal; and a gap retainingmember that is provided on the second substrate and retains an intervalbetween the first and second substrates.

[0046] In the above two electro-optical devices, the use of the gapretaining members provides the following advantages. First, it is notlonger necessary to use spacers. Second, since the height of the gapretaining members can be set as desired, the interval between thesubstrates can be determined as desired. Third, since the gap retainingmembers are fixed, they are not gathered unlike the conventionalspacers. Therefore, point defects do not occur.

[0047] In the above two electro-optical devices, the position of the gapretaining members can be set as desired. For example, the gap retainingmembers can be provided in an area that substantially confronts thepixel area. In this case, it is preferable that the gap retainingmembers be provided at locations that are not used for display, forinstance, on a black matrix of color filters and bus lines in the pixelarea. Alternatively, by providing the gap retaining members in an areathat does not confront the pixel area, the interval between thesubstrates can be retained without causing no influences on the display.

[0048] Where the invention is applied to an electro-optical device inwhich a first substrate (TFT substrate) is provided with a pixel areaand a driver circuit area having driver circuits for driving switchingelements that are provided in the pixel area, it is preferable that thegap retaining members be provided on a second substrate (opposedsubstrate) in an area that does not confront the driver circuit area. Inthis case, it is possible to prevent the driver circuits from beingdamaged or destroyed by stress that is imposed by the gap retainingmembers.

[0049] According to the invention, since the gap retaining members areprovided on the second substrate, influences (solvent or etchant-relatedinfluences, mechanical impact, etc.) of the formation of the gapretaining members do not affect the first substrate. Provided with thepixel area and the driver circuits, the first substrate has a muchhigher integration density than the second substrate. In view of this,the gap retaining members are provided on the second substrate tominimize the number of processes that are executed on the firstsubstrate.

[0050] Further, by providing the gap retaining members on the secondsubstrate, the conditions that are set in selecting a material arerelaxed. For example, where the invention is applied to a TFT-typeliquid crystal display device, since pixel TFTs and driver circuit TFTsare formed in the first substrate (TFT substrate), it is necessary toselect a material capable of providing a sufficiently large selectiveetching ratio to the material of those TFTs.

[0051] On the other hand, only such members as an opposed electrode andcolor filters are formed on the second substrate (opposed substrate),that is, the number of materials used in the second substrate is smallerthan in the first substrate. Thus, the number of conditions to be set inselecting a material is small. Further, a material such as that of anetching liquid, an etching gas, or the like and means that are necessaryto form the gap retaining members can be selected from wider ranges.

[0052] To make it possible to uniformize the interval between thesubstrates, it is preferable that the gap retaining members be made of aplanarization material capable of canceling out the asperity of the basemember. For example, the gap retaining members may be made of a resinmaterial selected from polyimide, acrylic, polyamide, andpolyimideamide, an ultraviolet curable resin, or a thermosetting resinas typified by an epoxy resin.

[0053] The above resin materials are frequently used as interlayerinsulating films of the TFT substrate (first substrate). In such a case,it is difficult to provide a large selective etching ratio if the gapretaining members made of a resin material are provided on the TFTsubstrate. This is the reason why in the invention the gap retainingmembers are formed on the opposed substrate (second substrate).

BRIEF DESCRIPTION OF THE DRAWINGS

[0054]FIGS. 1A-1B are top views of a TFT substrate and an opposedsubstrate, respectively, according to a first embodiment of the presentinvention;

[0055]FIGS. 2A-2E and 3A-3B show a manufacturing process of the TFTsubstrate according to the first embodiment;

[0056]FIGS. 4A-4D show a manufacturing process of gap retaining membersaccording to the first embodiment;

[0057]FIGS. 5A and 5B are a top view and a perspective view,respectively, of an active matrix liquid crystal display deviceaccording to the first embodiment;

[0058]FIG. 6 is a sectional view of the active matrix liquid crystaldisplay device according to the first embodiment;

[0059]FIGS. 7A-7D and 8A-8B show a manufacturing process of an activematrix liquid crystal display device according to a second embodiment ofthe invention;

[0060]FIG. 8C is an enlarged view of a gap retaining member according tothe second embodiment; FIG. 9 is a top view of the active matrix liquidcrystal display device according to the second embodiment;

[0061]FIG. 10 is a top view of an active matrix liquid crystal displaydevice according to a third embodiment of the invention;

[0062]FIGS. 11A-11C show a manufacturing process of an active matrixliquid crystal display device according to a fourth embodiment of theinvention;

[0063]FIG. 12A is a top view of the active matrix liquid crystal displaydevice according to the fourth embodiment;

[0064]FIG. 12B is an enlarged view showing a relationship between gapretaining members and a liquid crystal material flowing direction in thefourth embodiment;

[0065]FIGS. 13A-13C and 14A-14B show a process of forming gap retainingmembers according to a fifth embodiment of the invention;

[0066]FIGS. 15A and 15B are a top view and an enlarged perspective view,respectively, of an active matrix liquid crystal display deviceaccording to the fifth embodiment;

[0067]FIG. 16 is a top view of an active matrix liquid crystal displaydevice according to a sixth embodiment of the invention;

[0068]FIG. 17 is a top view of an active matrix liquid crystal displaydevice according to a seventh embodiment of the invention;

[0069]FIG. 18 is a schematic sectional view of a liquid crystal displaydevice according to a tenth embodiment of the invention;

[0070]FIG. 19 is a sectional view of a TFT substrate according to thetenth embodiment;

[0071]FIGS. 20A-20E show a manufacturing process of an opposed substrateaccording to the tenth embodiment;

[0072]FIGS. 21A and 21B are a top view and an enlarged perspective viewof the opposed substrate according to the tenth embodiment;

[0073]FIG. 22 is a top view of an opposed substrate according to athirteenth embodiment of the invention;

[0074]FIG. 23 is a top view of an opposed substrate according to afourteenth embodiment of the invention;

[0075]FIGS. 24A and 24B are top views of opposed substrates according toa fifteenth embodiment of the invention;

[0076]FIGS. 25A and 25B are a top view and an enlarged perspective view,respectively, of an opposed substrate according to a sixteenthembodiment of the invention;

[0077]FIG. 26 is a top view of another opposed substrate according tothe sixteenth embodiment;

[0078]FIG. 27 is a top view of an opposed substrate according to aseventeenth embodiment of the invention;

[0079]FIG. 28 is a schematic perspective showing the configuration of apassive matrix liquid crystal panel according to an eighteenthembodiment of the invention;

[0080]FIGS. 29A-29F and 30A-30B show a manufacturing process of thepassive matrix liquid crystal panel according to the eighteenthembodiment;

[0081]FIG. 31 is a schematic sectional view of the passive matrix liquidcrystal panel according to the eighteenth embodiment;

[0082]FIG. 32 is a top view of a substrate showing an arrangement of gapretaining members according to the eighteenth embodiment;

[0083]FIG. 33 is a top view of a substrate showing an arrangement of gapretaining members according to a modification of the eighteenthembodiment;

[0084]FIGS. 34A and 34B are a sectional view and a plan view,respectively, of a conventional active matrix liquid crystal displaydevice;

[0085]FIGS. 35A and 35B show a manufacturing process of the conventionalactive matrix liquid crystal display device;

[0086]FIG. 36 is a sectional view of a TFT substrate of the conventionalactive matrix liquid crystal display device; and

[0087]FIGS. 37A and 37B are sectional views of the conventional activematrix liquid crystal display device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

[0088] This embodiment will be described with reference to FIGS. 1A-1Bto 6. This embodiment is directed to a case where the invention isapplied to an active matrix liquid crystal display device. FIG. 1A is atop view of a TFT substrate and FIG. 1B is a top view of an opposedsubstrate.

[0089] As shown in FIG. 1A, a TFT substrate 100 consists of a substrate101 and a pixel area 102 and driver circuit areas 103 and 104 that areformed on the substrate 101. Pixel electrodes, TFTs that are connectedto the respective pixel electrodes, and other members are arranged inthe pixel area 102. Driver circuits for driving the TFTs in the pixelarea 102 are arranged in the driver circuit areas 103 and 104.

[0090] As shown in FIG. 1B, an opposed substrate 200 consists of asubstrate 201, an area 202 to confront the pixel area 102 of the TFTsubstrate 100, and areas 203 and 204 to confront the respective drivercircuit areas 103 and 104. The TFT substrate 100 and the opposedsubstrate 200 are bonded together with a sealing agent 205 that isprovided on a peripheral portion of the substrate 201. An opposedelectrode is formed in the pixel-confronting area 202 of the opposedsubstrate 200.

[0091] As shown in FIG. 6, the TFT substrate 100 and the opposedsubstrate 200 confront each other, a liquid crystal 300 is injectedthrough a liquid crystal injection inlet 206 into the space between thesubstrates 100 and 200, and the liquid crystal is sealed with a sealingagent 205. Alignment films for giving proper alignment to the liquidcrystal are formed to constitute the surfaces of the TFT substrate 100and the opposed substrate 200.

[0092] Next, a manufacturing method of the TFT substrate 100 will bedescribed with reference to FIGS. 2A-2E and 3A-3B. The right-handportions of FIGS. 2A-2E and 3A-3B show a manufacturing process of a TFTthat is to be formed in the pixel area 102 and the left-hand portionsshow a manufacturing process of TFTs to be formed in the driver circuitareas 103 and 104, respectively.

[0093] First, as shown in FIG. 2A, a silicon oxide film as an undercoatinsulating film 121 for preventing impurity diffusion from a glasssubstrate 101 is formed on the glass substrate 101 at a thickness of100-300 nm. The silicon oxide film may be formed by sputtering or plasmaCVD in an oxygen atmosphere. In this embodiment, a 200-nm-thick siliconoxide film is formed by plasma CVD by using a TEOS gas as a material. Ifa quartz substrate is used as the substrate 101, the undercoatinsulating film 121 can be omitted.

[0094] Then, an amorphous or polycrystalline silicon film is formed at athickness of 30-150 nm, preferably 50-100 nm, by plasma CVD or LPCVD. Tocrystallize the silicon film, thermal annealing is performed at atemperature higher than 500° C., preferably 800-900° C. After thesilicon film is crystallized by thermal annealing, optical annealing maybe performed to improve the crystallinity. Further, as disclosed inJapanese Unexamined Patent Publication No. Hei. 6-244104, thecrystallization of silicon may be accelerated by adding such an elementas nickel (catalyst element) in crystallizing the silicon film bythermal annealing.

[0095] In this embodiment, after a 50-nm-thick amorphous silicon film isformed by plasma CVD, hydrogen is removed by performing a heat treatmentat 450° C. for one hour and then the amorphous silicon film is convertedinto a polycrystalline silicon film by illuminating it with excimerlaser light. The polycrystalline silicon film is patterned intoisland-like active layers (a p-channel TFT active layer 122 and ann-channel TFT active layer 123) of peripheral driver circuit TFTs and anisland-like active layer 124 of a pixel TFT. Although for convenienceFIGS. 2A-2E show only three TFTs, actually millions of TFTs are formedat the same time.

[0096] A gate insulating film 125 is then formed. In this embodiment, a120-nm-thick insulating film is formed by plasma CVD by using, as amaterial gas, a mixed gas of dinitrogen monoxide (N₂O) and monosilane(SiH₄).

[0097] Thereafter, a 300-nm-thick aluminum film is formed by sputteringand then patterned into gate electrodes 126-128.

[0098] Then, as shown in FIG. 2B, all the island-like active layers122-124 are doped with phosphorus ions in a self-aligned manner by iondoping with the gate electrodes 126-128 used as a mask. Phosphine (PH₃)is used as a doping gas and the dose is set at 1×10¹² to 5×10¹³atoms/cm². As a result, weak n-type regions (n⁻ regions) 129-131 areformed.

[0099] Then, as shown in FIG. 2C, a photoresist mask 132 is formed so asto cover the entire p-channel TFT active layer 122 and a photoresistmask 134 is formed so as to cover part of the pixel TFT active layer124. The mask 134 is formed so as to cover a portion that ends atpositions distant from the respective ends of the gate electrode 128 by3 μm as measured parallel with the gate electrode 128.

[0100] Then, phosphorus ions are again implanted by ion doping.Phosphine is used as a doping gas and the dose is set at 1×10¹⁴ to5×10¹⁵ atoms/cm². As a result, sources/drains 135 and 136 are formed asstrong n-type regions (n⁺ regions). In this doping step, no phosphorusions are implanted into regions 137, covered with the mask 134, of theweak n-type regions (n⁻ regions) 131 of the pixel TFT active layer 124.Therefore, the regions 137 remain of the weak n type. The width x of thelow-concentration impurity regions 137 is about 3 μm.

[0101] Then, as shown in FIG. 5D, the n-channel TFT active layers 123and 124 are covered with a photoresist mask 138. Thereafter, boron isimplanted into the island-like region 122 by ion doping by usingdiborane (B₂H₆) as a doping gas. The dose is set at 5×10¹⁴ to 8×10¹⁵atoms/cm². Since the boron dose in this doping is higher than thephosphorus dose in the doping of the step of FIG. 2B, the weak n-typeregions 130 are inverted to strong p-type regions 139.

[0102] Subsequently, thermal annealing is performed at 450°-850° C. for0.5-3 hours to activate the doping impurities and restore thecrystallinity of silicon. As a result of this thermal annealing step,damage of the silicon film that has been caused by the doping steps isrepaired.

[0103] As a result of the above doping steps, an n-type TFT having thestrong n-type regions 135 as a source and a drain and a p-type TFThaving strong p-type regions 139 as a source and a drain are formed inthe driver circuit area 103 (104). Further, an n-type TFT having thestrong n-type regions 136 as a source and a drain and the weak n-typelow-concentration impurity regions 137 is formed in the pixel area 102(see FIG. 2D).

[0104] Then, a first interlayer insulating film 140 is formed as shownin FIG. 2E. In this embodiment, a 500-nm-thick silicon nitride film isformed by plasma CVD. The first interlayer insulating film 140 may beanother type of single layer film such as a silicon oxide film or asilicon oxynitride film, or a multilayered film of a silicon nitridefilm and a silicon oxide film or of a silicon nitride film and a siliconoxynitride film. Thereafter, contact holes are formed through the firstinterlayer insulating film 140 by etching it.

[0105] Thereafter, a titanium/aluminum/titanium multilayered film isformed by sputtering and then etched into driver circuitelectrodes/interconnections 141-143 and pixel TFTelectrodes/interconnections 144 and 145. In this embodiment, thethickness of each titanium film is set at 100 nm and the thickness ofthe aluminum film is set at 300 nm.

[0106] Then, as shown in FIG. 3A, an organic resin film as a secondinterlayer insulating film 146 is formed at a thickness of 1.0-2.0 μm.The organic resin may be polyimide, polyamide, polyimideamide,polyacrylic, or the like. In this embodiment, a 1.5-μm-thick polyimidefilm is formed as the second interlayer insulating film 146. Then, acontact hole reaching the pixel TFT electrode 525 is formed byphotolithography. Thereafter, as shown in FIG. 3B, a pixel electrode 147is formed by forming a 300-nm-thick aluminum film to which titanium isadded at 1 wt % and then patterning it.

[0107] In the pixel area 102 of the TFT substrate 100 shown in FIG. 18A,at least one TFT is provided for and electrically connected to eachpixel electrode. Examples of driver circuits formed in the drivercircuit areas 103 and 104 are a shift register and an address decoder.Other circuits may also be formed when necessary.

[0108] In this manner, driver circuit TFTs and pixel TFTs are formed inan integral manner in the driver circuit areas 103 and 104 and the pixelarea 102, respectively. In this embodiment, the number of pixels is setat 1,024 (vertical)×768 (horizontal). In this specification, an areawhere pixel TFTs including the end pixel TFTs exist is called the pixelarea 102 and an area where driver circuit TFTs including the end drivercircuit TFTs exist is called the driver circuit area 103 (104).

[0109] The TFT substrate 100 is cleaned sufficiently to remove variouschemicals such as etching liquids and resist removers that were used forthe surface processing in forming the TFTs.

[0110] Next, a process of forming gap retaining members will bedescribed. In the following description, the configurations of thedriver circuit areas 103 and 104 where driver circuit TFTs 160 areformed and the pixel area 102 where pixel TFTs 150 are formed aresimplified as shown in FIGS. 4A-4D. In FIGS. 4A-4D, for convenience, thescales of the respective parts are different.

[0111] First, as shown in FIG. 4B, a 2.2-μm-thick photosensitivepolyimide film 301 is formed by spin coating. Thereafter, the substrateis left at the room temperature for 30 minutes to uniformize thethickness of the photosensitive polyimide film 301 over the entire TFTsubstrate 100 (leveling). Then, the TFT substrate 100 on which thephotosensitive polyimide film 301 is formed is pre-baked at 120° C. for3 minutes.

[0112] Then, the photosensitive polyimide film 301 is patterned in thefollowing manner. As shown in FIG. 4C, after the photosensitivepolyimide film 301 is covered with a photomask 302, ultraviolet light isapplied to the TFT substrate 100 from above. Subsequently, developmentis performed and then post-baking is performed at 280° C. for one hour.Patterned gap retaining members 303 are thus formed as shown in FIG. 4D.

[0113]FIG. 5A is a top view of the TFT substrate according to thisembodiment, and FIG. 5B is an enlarged perspective view of a part of theTFT substrate that is indicated by a broken line in FIG. 5A. In FIGS. 5Aand 5B, for convenience, the scales of the gap retaining members 303,the pixel area 102, and the driver circuit areas 103 and 104 aredifferent from each other. In this embodiment, as shown in FIGS. 5A and5B, the gap retaining members 303 are shaped like a cylinder of 10 μm indiameter and 2.2 μm in height. The gap retaining members 303 are formedat regular intervals of 30 μm so as to surround the pixel area 102 at adistance of about 70 μm from the end pixel TFTs. The arrangement densityof the gap retaining members 303 in the vicinity of the liquid crystalinjection inlet is set lower than in the other portions. It ispreferable that the arrangement density of the gap retaining members 303be uniform.

[0114] In the gap retaining members 303 of the invention, the accuracyof their height is important. In this embodiment, the height accuracy ofthe gap retaining members 303 is set at ±0.1 μm. On the other hand, itis sufficient that the positional accuracy of the gap retaining members303 be about +10 μm. In this embodiment, part of the gap retainingmembers 303 are formed between the pixel area 102 and the driver circuitareas 103 and 104. In this embodiment, the intervals between the pixelarea 102 and the driver circuit areas 103 and 104 are about 400 nm,which is sufficiently longer than the diameter of the gap retainingmembers 303. Therefore, the positional accuracy of the gap retainingmembers 303 is not much important. The gap retaining members 303 are notformed inside the pixel area 102 and the driver circuit areas 103 and104.

[0115] Although in this embodiment the gap retaining members 303 areshaped like a cylinder, they may be shaped like an ellipse, astreamlined shape, or a polygon such as a triangle or a rectangle. Thegap retaining members 303 may have any shape as long as they can controlthe gap between the TFT substrate (first substrate) 100 and the opposedsubstrate (second substrate) 200. Although in this embodiment all thegap retaining members 303 have the same shape and are arranged atregular intervals, gap retaining members having plural kinds of shapesmay be arranged at different intervals. Although in this embodiment thegap retaining members 303 are formed at the constant distance from thepixel area 102, they may be formed at different distances from pixelarea 102. Further, although in this embodiment the gap retaining members303 are formed so as to surround the pixel area 102, they may be formedanywhere except the insides of the pixel area 102 and the driver circuitareas 103 and 104 as long as they can control the cell gap.

[0116] Then, alignment films are formed on the TFT substrate 100 and theopposed substrate 200. Specifically, the TFT substrate 100 and theopposed substrate 200 are coated with polyimide-type vertical alignmentfilms by one of spin coating, flexography, and screen printing. In thisembodiment, 1,000-Å-thick alignment films are formed by spin coating.Then, the alignment films are cured by baking in which a hot wind of180° C. is fed.

[0117] Then, rubbing is performed in which the surface of the opposedsubstrate 200, i.e., the surface of the alignment film, is rubbed in onedirection with a buff cloth (fiber of rayon, nylon, or the like) havinghair lengths of 2-3 mm. In this embodiment, rubbing is not performed onthe TFT substrate 100 side.

[0118] Thereafter, a sealing agent 205 is applied to the opposedsubstrate 200 along its periphery (see FIG. 1B). Alternatively, thesealing agent 205 may be applied to the TFT substrate 100 side. The TFTsubstrate 100 and the opposed substrate 200 are then bonded together(see FIG. 6).

[0119] Then, a liquid crystal material 300 as a display medium isinjected through a liquid crystal injection inlet 206, whereby theliquid crystal material 300 is held between the TFT substrate 100 andthe opposed substrate 200. In this embodiment, since the gap retainingmembers 303 are shaped like a cylinder, the flow resistance that occursbetween the liquid crystal material 300 and the surfaces of the gapretaining members 303 in injecting the liquid crystal material 300 issmall. Therefore, the liquid crystal material 300 can be injecteduniformly over the entire substrate surfaces. It is preferable that thegap retaining members 303 be shaped and arranged so as to reduce theflow resistance.

[0120] Then, after a sealing agent (not shown) is applied to the liquidcrystal injection inlet 206, the sealing agent is cured by illuminatingit with ultraviolet light. The liquid crystal material 300 is thuscompletely sealed in the cell.

[0121] When the display characteristics of cells actually manufacturedin the above manner were checked, no interference fringe was observed onthe cell surfaces. Further, superior display performance with nodisclination was obtained.

Embodiment 2

[0122] In this embodiment, the steps until pixel TFTs and driver circuitTFTs are formed to constitute a TFT substrate are the same as in thefirst embodiment and hence are not described here.

[0123] After the pixel TFTs and the driver circuit TFTs are formed in anintegral manner to constitute the TFT substrate, gap retaining membersare formed on the TFT substrate as shown in FIG. 3B. A process offorming gap retaining members according to this embodiment will bedescribed below with reference to FIGS. 7A-7D and 8A-8C. Theconfiguration of FIG. 7A is the same as that of FIG. 4A.

[0124] First, as shown in FIG. 7B, a 2.2-μm-thick photosensitivepolyimide film 311 is formed by spin coating. Thereafter, the substrateis left at the room temperature for 30 minutes to uniformize thethickness of the photosensitive polyimide film 311 over the entire TFTsubstrate 100 (leveling). Then, the TFT substrate 100 on which thephotosensitive polyimide film 311 is formed is pre-baked at 120° C. for3 minutes.

[0125] Then, the photosensitive polyimide film 311 is patterned in thefollowing manner. As shown in FIG. 7C, after the photosensitivepolyimide film 311 is covered with a photomask 312, ultraviolet light isapplied to the TFT substrate 100 from above. Subsequently, developmentis performed, the photomask 312 is removed, and then post-baking isperformed at 280° C. for one hour. As a result, cylindrical gapretaining members 313 are formed (see FIG. 7D).

[0126] Thereafter, a resist film is applied uniformly and patterned intoa desired pattern. In this embodiment, a resist film (not shown) isformed on the top faces of the cylindrical gap retaining members 313.Subsequently, as shown in FIG. 8A, the shape of the gap retainingmembers 313 is modified by applying oxygen plasma to those. Since thetop surfaces of the gap retaining members 313 are protected by theresist film (not shown), only their side faces are etched (ashed),whereby gap retaining members 314 having tapered side faces are formedas shown in FIG. 8B. After completion of the etching, the resist film isremoved. FIG. 8C is an enlarged view of a gap retaining member 314. Eachgap retaining member 314 is shaped like a truncated cone in which thebottom face diameter is 30 μm, the top face diameter is 20 μm, and theheight is 2.2 μm.

[0127]FIG. 9 is a top view of the TFT substrate 100 according to thisembodiment. The patterned cell gas retaining members 314 have beenformed by the above process. In this embodiment, as shown in FIG. 9, thegap retaining members 314 are formed so as to doubly surround the pixelarea 102.

[0128] Thereafter, alignment films are formed on the TFT substrate 100and the opposed substrate 200 in the same manner as in the firstembodiment.

[0129] Then, rubbing is performed on the surface of the opposedsubstrate 200, i.e., the surface of the alignment film, and a sealingagent 315 is applied to the TFT substrate 100 (see FIG. 9). The TFTsubstrate 100 and the opposed substrate 200 are then bonded together(not shown). In FIG. 9, the same reference numerals as in FIGS. 1A and1B denote the same members as in FIGS. 1A and 1B.

[0130] Then, a liquid crystal material as a display medium is injectedthrough a liquid crystal injection inlet. In this embodiment, since theside faces of the gap retaining members 314 are tapered, the resistancethat occurs between the liquid crystal material and the gap retainingmembers 314 in injecting the liquid crystal material is small.Therefore, the liquid crystal material can be injected uniformly overthe entire substrates. Then, the liquid crystal material is completelysealed in the cell by sealing the liquid crystal injection inlet with asealing agent (not shown).

[0131] The uniformity of the cell thickness can be improved byincreasing the number of gap retaining members 314, particularly byincreasing the number of gap retaining members 314 in the vicinity ofthe pixel area 102. When the display characteristics of cells actuallymanufactured in the above manner were checked, no interference fringewas observed on the cell surfaces. Further, superior display performancewith no disclination was obtained.

Embodiment 3

[0132] This embodiment is different from the first embodiment only inthe number and arrangement of gap retaining members. Since thisembodiment is the same as the first or second embodiment in the otherpoints, a manufacturing process will not be described. In FIG. 10, thesame reference numerals as in FIGS. 1A and 1B and FIG. 9 denote the samemembers as in the latter figures. In this embodiment, a sealing agent403 is formed on the TFT substrate 100 side.

[0133] In this embodiment, as shown in FIG. 10, gap retaining members401 are formed on the TFT substrate 100 so as to surround the pixel area102 and gap retaining members 402 are formed on the TFT substrate 100 soas to surround the driver circuit areas 103 and 104. The gap retainingmembers 401 and 402 are shaped like a cylinder of 30 μm in diameter and2.2 μm in height.

[0134] Then, rubbing is performed on the surface of the opposedsubstrate 200, i.e., the surface of an alignment film, and a sealingagent 403 is applied to the TFT substrate 100 (see FIG. 10). The TFTsubstrate 100 and the opposed substrate 200 are then bonded together(not shown).

[0135] Then, a liquid crystal material as a display medium is injectedthrough a liquid crystal injection inlet 404, and the liquid crystalmaterial is completely sealed in the cell by sealing the liquid crystalinjection inlet 404 with a sealing agent (not shown).

[0136] When the display characteristics of cells actually manufacturedin the above manner were checked, no interference fringe was observed onthe cell surfaces. Further, superior display performance with nodisclination was obtained.

Embodiment 4

[0137] In this embodiment, the steps until pixel TFTs and driver circuitTFTs are formed to constitute a TFT substrate are the same as in thefirst embodiment and hence are not described here.

[0138] A TFT substrate 100 is produced as shown in FIG. 3B according thesteps described in the first embodiment. A process of forming gapretaining members according to this embodiment will be described belowwith reference to FIGS. 11A-11C.

[0139] The configuration of FIG. 11A is the same as that of FIG. 3B. Inthis embodiment, gap retaining members 503 are formed by printing on theTFT substrate 100 in which pixel TFTs 150 and driver circuit TFTs 160are formed. In this embodiment, the gap retaining members 503 are madeof a polyimide resin.

[0140] Specifically, as shown in FIG. 11B, gap retaining members 503 areformed by covering the TFT substrate 100 with a screen 501 and thenprinting a polyimide resin. In this embodiment, gap retaining members503 of 1.1 μm in height are formed by a single printing operation. Gapretaining members 503 having a desired height are formed by repeatingthe steps of printing a polyimide resin, baking it for a while, andagain printing a polyimide resin so that it is superimposed on theprevious polyimide resin.

[0141]FIG. 12A is a top view showing the TFT substrate 100 on which thegap retaining members 503 are formed. In FIG. 12A, the same referencenumerals as in FIGS. 1A and 1B and FIG. 9 denote the same members as inthe latter figures. In this embodiment, a sealing member 511 is formedon the TFT substrate 100 side.

[0142] In this embodiment, the gap retaining members 503 are shaped likean elliptical pole in which the major axis length is 30 μm, the minoraxis length is 15 μm, and the height is 2.2 μm, and are arranged so asto surround the pixel area 102. Further, in this embodiment, the gapretaining members 503 are arranged so as to reduce the resistance thatoccurs between the gap retaining members 503 and a liquid crystalmaterial in injecting the liquid crystal material. That is, the gapretaining members 503 are arranged so that the major axes of the gapretaining members 503 are parallel with the flowing direction of theliquid crystal material that is injected through a liquid crystalinjection inlet (see FIG. 12B).

[0143] Then, alignment films are formed on the surfaces of the TFTsubstrate 100 and the opposed substrate 200. Specifically, the TFTsubstrate 100 and the opposed substrate 200 are coated with100-nm-thick, polyimide-type vertical alignment films (not shown) by oneof spin coating, flexography, and screen printing. Then, the alignmentfilms are cured by baking in which a hot wind of 180° C. is fed.

[0144] Thereafter, a sealing agent 511 is applied to a peripheralportion of the TFT substrate 100 so as to leave a liquid crystalinjection inlet 512, and the TFT substrate 100 and the opposed substrate200 are bonded together (not shown).

[0145] Then, a liquid crystal material is injected through the liquidcrystal injection inlet 512. In this embodiment, the gap retainingmembers 503 are shaped like an elliptical pole and are arranged so as toreduce the resistance that occurs between the gap retaining members 503and the liquid crystal material in injecting the liquid crystalmaterial. Therefore, the liquid crystal material can be injecteduniformly over the entire substrates.

[0146] Thereafter, a sealing agent (not shown) is applied to the liquidcrystal injection inlet 512 and then cured by illuminating it withultraviolet light. The liquid crystal material is thus completely sealedin the cell.

Embodiment 5

[0147] This embodiment is directed to a method of forming gap retainingmembers that is different from in the first embodiment.

[0148] First, a TFT substrate 100 is produced according to the stepsdescribed in the first embodiment. The TFT substrate 100 is cleanedsufficiently to remove various chemicals such as etching liquids andresist removers that were used for the surface processing in forming theTFTs.

[0149] Next, a process of forming gap retaining members will bedescribed with reference to FIGS. 13A-13C and 14A-14B. In these figures,for convenience, the scales of gap retaining members formed and the TFTsare made different from each other.

[0150]FIG. 13A shows the TFT substrate 100 that has been produced by thesteps of the first embodiment. The configuration of FIG. 13A correspondsto that of FIG. 3B. Some reference numerals are omitted in FIG. 13A.

[0151] As shown in FIG. 13B, a 4.2-μm-thick photosensitive polyimidefilm 601 is formed by spin coating. Thereafter, the substrate is left atthe room temperature for 30 minutes to uniformize the thickness of thephotosensitive polyimide film 601 over the entire TFT substrate 100(leveling). Then, the TFT substrate 100 on which the photosensitivepolyimide film 601 is formed is pre-baked at 120° C. for 3 minutes.

[0152] Then, the top surface of the photosensitive polyimide film 601 isplanarized by polishing it by CMP (chemical mechanical polishing). Inthis embodiment, slurry that is used in the CMP step is a colloid-likeone in which a silica (SiO₂) fine powder is dispersed in an acidsolution. As for the CMP conditions, each of the substrate and anabrasive cloth is rotated at 50 rpm and the polishing time is set at 3minutes. The top surface of the photosensitive polyimide film 601 isplanarized by the CMP step. The thickness of the planarizephotosensitive polyimide film 601 was 3.2 μm. The CMP processingaccuracy of the photosensitive polyimide film 601 was 0.1 μm.

[0153] Although in this embodiment the slurry that is used in the CMPstep is one in which a silica fine powder is dispersed in an acidsolution, slurry obtained by dispersing aluminum oxide (Al₂O₃), ceriumoxide (CeO), or the like in an acid solution ray also be used. It isdesirable that the slurry be changed in accordance with the materialthat is subjected to CMP. Further, although in this embodiment CMP isperformed for 3 minutes while each of the substrate and the abrasivecloth is rotated at 50 rpm, it is desirable that the optimum rotationspeed and processing time be set for a material to be subjected to CMP.

[0154] The cell gap (interval between the substrates) is determined bythe thickness of the photosensitive polyimide film 601 that has beensubjected to CMP. Therefore, the thickness of the as-formedphotosensitive polyimide film 601 may be set properly and the thicknessto be reduced by CMP may be adjusted in accordance with the desired cellgap. In this manner, the desired cell gap can be obtained with highaccuracy.

[0155] Although in this embodiment CMP is used in the step of polishingand planarizing the photosensitive polyimide film 601, this step may beexecuted by any method as long as the top surface of the photosensitivepolyimide film 601 can be planarized with high accuracy. For example,etch back may also be used.

[0156] Then, the photosensitive polyimide film 601 is patterned.Specifically, as shown in FIG. 14A, after the photosensitive polyimidefilm 601 is covered with a photomask 602, ultraviolet light is appliedto the TFT substrate 100 from above. Subsequently, development isperformed and then post-baking is performed at 280° C. for one hour. Asa result, patterned gap retaining members 603 are formed as shown inFIG. 14B. In this specification, the CMP-processed faces of the gapretaining members are called top faces.

[0157]FIG. 15A is a top view of the TFT substrate 100 according to thisembodiment. FIG. 15B is an enlarged perspective view of a part of FIG.15A that is indicated by a two-dot chain line. In FIGS. 15A and 15B, forconvenience, the scales of the gap retaining members 603, the pixel area102, and the driver circuit areas 103 and 104 are different from eachother. The components in FIGS. 15A and 15B that are given the samereference numerals as in FIGS. 1A and 1B are the same as thecorresponding components in FIGS. 1A and 1B.

[0158] In this embodiment, as shown in FIGS. 15A and 15B, the gapretaining members 603 are shaped like a cylinder of 4 μm in diameter and3.2 μm in height. In this embodiment, the gap retaining members 603 arearranged randomly. Their arrangement density may be set at 40-160 mm⁻².In this embodiment, it is set at 50 mm⁻².

[0159] Although in this embodiment the gap retaining members 603 areshaped like a cylinder, they may be shaped like an ellipse, astreamlined shape, or a polygon such as a triangle or a rectangle. Thegap retaining members 603 may have any shape as long as they can controlthe gap between the TFT substrate (first substrate) 100 and the opposedsubstrate (second substrate) 200. Although in this embodiment all thegap retaining members 603 have the same shape, gap retaining membershaving plural kinds of shapes may be formed. Further, although in thisembodiment the gap retaining members 603 are formed so that theirarrangement density is uniform over the entire surface of the TFTsubstrate 100, the gap retaining members 603 may be arranged at a higherdensity in a certain region.

[0160] Then, an opposed substrate 200 in which an opposed electrode isformed is prepared (see FIG. 1B). In this embodiment, the opposedelectrode that is formed in a pixel-confronting area 202 is made of ITO(indium tin oxide).

[0161] Then, alignment films (not shown) are formed on the TFT substrate100 and the opposed substrate 200. Specifically, the TFT substrate 100and the opposed substrate 200 are coated with 1,000-Å-thick,polyimide-type vertical alignment films by spin coating. Then, thealignment films are cured by baking in which a hot wind of 180° C. isfed.

[0162] Then, rubbing is performed in which the surface of the opposedsubstrate 200, i.e., the surface of the alignment film, is rubbed in onedirection with a buff cloth (fiber of rayon, nylon, or the like) havinghair lengths of 2-3 mm. In this embodiment, rubbing is not performed onthe TFT substrate 100 side.

[0163] Thereafter, in this embodiment, a sealing agent 605 is applied tothe opposed substrate 200 along its periphery so as to leave a liquidcrystal injection inlet 606 (see FIG. 15A). The TFT substrate 100 andthe opposed substrate 200 are then bonded together.

[0164] Then, a liquid crystal material as a display medium is injectedthrough the liquid crystal injection inlet 606, whereby the liquidcrystal material is held between the TFT substrate 100 and the opposedsubstrate 200. In this embodiment, since the gap retaining members 606are shaped like a cylinder, the flow resistance that occurs between theliquid crystal material and the surfaces of the gap retaining members603 in injecting the liquid crystal material is small. Therefore, theliquid crystal material can be injected uniformly over the entiresubstrate surfaces. It is preferable that the gap retaining members 603be shaped and arranged so as to reduce the flow resistance.

[0165] Then, after a sealing agent (not shown) is applied to the liquidcrystal injection inlet 606, the sealing agent is cured by illuminatingit with ultraviolet light. The liquid crystal material is thuscompletely sealed in the cell.

[0166] When the display characteristics of cells actually manufacturedin the above manner were checked, no interference fringe was observed onthe cell surfaces. Further, superior display performance with nodisclination was obtained.

Embodiment 6

[0167] This embodiment is different from the fifth embodiment in thearea where gap retaining members are formed. This embodiment will bedescribed with reference to FIG. 16. The components in FIG. 16 that aregiven the same reference numerals as in FIGS. 15A and 15B are the sameas the corresponding components in FIGS. 15A and 15B. Reference numeral610 denotes gap retaining members; 101, a substrate; 102, a pixel area;103 and 104, driver circuit areas; 605, a sealing agent; and 606, aliquid crystal injection inlet.

[0168] In this embodiment, as shown in FIG. 16, the gap retainingmembers 610 are formed at regular intervals in the pixel area 102 andthe driver circuit areas 103 and 104. It is preferable that in the pixelarea 102 the gap retaining members 610 be formed in regions where signallines and selection lines for the TFTs cross each other. The intervalbetween the gap retaining members 610 in the pixel area 102 may be madedifferent than in the driver circuit areas 103 and 104.

Embodiment 7

[0169] This embodiment is different from the second and fifthembodiments in the area where gap retaining members are formed. Thisembodiment will be described with reference to FIG. 17. The componentsin FIG. 17 that are given the same reference numerals as in FIGS. 15Aand 15B are the same as the corresponding components in FIGS. 15A and15B.

[0170] In this embodiment, as shown in FIG. 17, gap retaining members620 are formed in an area excluding the pixel area 102 and the drivercircuit areas 103 and 104.

[0171] In this embodiment, since the gap retaining members 620 do notexist in the pixel area 102 nor the driver circuit areas 103 and 104,they do not decrease the effective aperture ratio as well as unnecessarystress is not exerted on the TFTs in the pixel area 102 and the drivercircuit areas 103 and 104 in bonding the TFT substrate 100 and theopposed substrate 200 together. Therefore, the TFTs are not damaged andhence the yield of products will increase.

Embodiment 8

[0172] This embodiment is the same as the fifth, sixth, and seventhembodiment in the configuration of the TFT substrate 100 side, and isdifferent from those embodiment in the configuration of the opposedsubstrate 200 side.

[0173] In an electro-optical device according to this embodiment, anorganic resin film is formed after an opposed electrode is formed toconstitute the opposed substrate 100. The organic resin film serves as aleveling film. In this embodiment, the organic resin film is made ofpolyimide. Other examples of the material of the organic resin film areacrylic, polyamide, and polyimideamide and the like.

[0174] Then, CMP is performed on the organic resin film in the samemanner as in the fifth embodiment, whereby the organic resin film isleveled.

[0175] Thereafter, alignment films are formed on the TFT substrate 100and the opposed substrate 200 and then rubbing is performed on theopposed substrate 200 side. The ensuing steps are the same as in thefifth embodiment.

[0176] In this embodiment, not only do the top faces of the gapretaining members provided on the TFT substrate 100 exist in the sameplane but also the flatness of the top surface of the organic resin filmprovided on the opposed substrate 200 is secured. Therefore, theuniformity of the cell gap can even be improved. The opposed substrate200 of this embodiment may be used in each of the first to fourthembodiments.

Embodiment 9

[0177] Although the first to eighth embodiments are directed to the caseof using planar TFTs, naturally the invention is not limited by the TFTstructure. Therefore, each TFT in the pixel area 102 and the drivercircuit areas 103 and 104 may be an inverted staggered structure TFT ora multi-gate TFT.

[0178] Although in the first to eighth embodiments the gap retainingmembers are made of polyimide, other resins such as acrylic, polyamide,and polyimideamide may also be used. Further, the gap retaining membersmay be made of a thermosetting resin.

[0179] Although in the first to eighth embodiments the gap retainingmembers are formed on the TFT substrate 100, they may be formed on theopposed substrate 200 or both of them. Even in such cases the gapretaining members may be formed according to the method of the fifthembodiment.

[0180] Although in the first to eighth embodiments the gap retainingmembers are made of polyimide, they may be made of other insulativematerials.

[0181] Although the first to eighth embodiments are directed to thereflection-type electro-optical devices, transmission-typeelectro-optical devices may be formed by making some modifications suchas using a transparent pixel electrode.

[0182] Although the first to eighth embodiments are directed to the casewhere a liquid crystal material is used as a display medium, the gapretaining members of the invention can also be with a mixed layer of aliquid crystal material and a polymer, that is, they can be used in apolymer dispersion type liquid crystal display device. Further, theelectro-optical devices of the invention may use any other display mediawhose optical characteristic is modulated in response to the applicationvoltage, such as an electroluminescence element.

[0183] Although in the first to eighth embodiments no particularreference is made to color display, color filters may be provided on theopposed substrate 200 side when color display is needed. The colorfilters are required to be uniform in thickness, i.e., flat, andsuperior in both heat resistance and resistance to chemicals.

[0184] Although in the first to eighth embodiments rubbing is performedon only the opposed substrate 200 side, rubbing may be performed on theTFT substrate 100 side or both substrates.

[0185] Although the first to eighth embodiments are directed to theactive matrix electro-optical devices, it goes without saying that theinvention can be applied to passive electro-optical devices that have noactive elements such as TFTs.

Embodiment 10

[0186] This embodiment will be described with reference to FIGS. 18 toFIGS. 21A and 21B. This embodiment is directed to a case where theinvention is applied to an active matrix liquid crystal display deviceand gap retaining members are formed on only the opposed substrate 200.FIG. 18 is a schematic sectional view of a liquid crystal displaydevice. The components in FIG. 18 that are given the same referencenumerals as in FIGS. 1A and 1B are the same components as in FIGS. 1Aand 1B.

[0187] As shown in FIG. 18, a TFT substrate 100 and an opposed substrate200 are bonded together with a sealing agent 205 that is provided on aperipheral portion of a substrate 201. The opposed substrate 200 isprovided with an opposed electrode 210 that confronts a pixel area 102and gap retaining members 220 for retaining the gap between the TFTsubstrate 100 and the opposed substrate 200.

[0188] A liquid crystal 300 is injected into the space between the TFTsubstrate 100 and the opposed substrate 200 through a liquid crystalinjection inlet 206 and then sealed with a sealing agent 205. The TFTsubstrate 100 and the opposed substrate 200 are provided with alignmentfilms 110 and 230 for giving proper alignment to the liquid crystal 300,respectively.

[0189] First, the TFT substrate 100 is produced according to themanufacturing method of the TFT substrate 100 described in the firstembodiment (see FIGS. 2A-2E and 3A-3B). In the pixel area 102 of the TFTsubstrate 100 shown in FIG. 19, at least one TFT is provided for andelectrically connected to each pixel electrode. Examples of drivercircuits formed in the driver circuit areas 103 and 104 are a shiftregister and an address decoder. Other circuits may also be formed whennecessary.

[0190] After the configuration of FIG. 3B is obtained, the TFT substrate100 is cleaned sufficiently to remove various chemicals such as etchingliquids and resist removers that were used for the surface processing informing the TFTs. Then, an alignment film 110 is formed on the TFTsubstrate 100 as shown in FIG. 19 according to a method described later.

[0191] Next, a manufacturing process of the opposed substrate 200 willbe described with reference to FIGS. 20A-20E. As shown in FIG. 20A, atransparent glass or quartz substrate is used as a substrate 201. Inthis embodiment, a glass substrate is used. A transparent conductivefilm is formed on the glass substrate 201 and then patterned into anopposed electrode 210 in an area 202 to confront the pixel area 102 (seeFIG. 20A). In this embodiment, a 150-nm-thick ITO film is formed as thetransparent conductive film.

[0192] If necessary, color filters and a black matrix are formed by aknown method such as dyeing or printing before the formation of theopposed electrode 210. The color filters are required to be uniform inthickness, i.e., flat, and superior in both heat resistance andresistance to chemicals.

[0193] Next, a process of forming the gap retaining members 220 will bedescribed. In this embodiment, the gap retaining members 220 are formedby using polyimide which is one of photosensitive resin materials.

[0194] First, as shown in FIG. 20B, a 3.2-μm-thick photosensitivepolyimide film 211 is formed by spin coating. Thereafter, the substrateis left at the room temperature for 30 minutes to uniformize thethickness of the photosensitive polyimide film 211 over the entireopposed substrate 200 (leveling). Then, the opposed substrate 200 onwhich the photosensitive polyimide film 211 is formed is pre-baked at120° C. for 3 minutes.

[0195] Since the thickness of the photosensitive polyimide film 211determines the cell gap (interval between the substrates), it may be setproperly in accordance with the desired cell gap. For example, thethickness of the photosensitive polyimide film 211 may be determined sothat the cell gas becomes about 4-6 μm for a transmission-type liquidcrystal display device, about 2-3 μm for a reflection-type liquidcrystal display device, and less than 2 μm for a ferroelectric liquidcrystal display device. Since the liquid crystal display device of thisembodiment is of a reflection type, the thickness of the photosensitivepolyimide film 211 is set at 3.2 μm.

[0196] Then, the photosensitive polyimide film 211 is patterned.Specifically, after the photosensitive polyimide film 211 is coveredwith a photomask 212 as shown in FIG. 20C, ultraviolet light is appliedfrom the mask 212 side. Subsequently, development is performed and thenpost-baking is performed at 280° C. for one hour. Patterned gapretaining members 220 are thus formed as shown in FIG. 20D.

[0197]FIGS. 21A and 21B are a top view and an enlarged perspective view,respectively, of the opposed substrate 200 in the state of FIG. 20D. Asshown in FIGS. 21A and 21B, the gap retaining members 220 are shapedlike a cylinder and replace the conventional spherical spacers.Therefore, the cylinder diameter and height of the gap retaining members220 may be set at 1.5-2.5 μm and 2.0-5.0 μm, respectively. In thisembodiment, the cylinder diameter is set at 3.0 μm and, to provide acell gap of 3.0 μm, the cylinder height is set at 3.2 μm in thepixel-confronting area 202. The height of the gap retaining members 220in driver-circuit-confronting areas 203 and 204 is made greater than inthe pixel-confronting area 202 by the total thickness of the opposedelectrode 210, the color filters, etc.

[0198] In this embodiment, the gap retaining members 220 are arrangedrandomly so as to function in the same manner as the conventionalspherical spacers. Therefore, the density of the gap retaining members220 may be set approximately equal to that of the conventional sphericalspacers, i.e., about 40-160 mm⁻². In this embodiment, the gap retainingmembers 220 are arranged randomly at a density of 50 mm⁻². Since the gapretaining members 220 are arranged randomly over the entire opposedsubstrate 200, the positional accuracy of the gap retaining members 220is not very important, which means a large production margin.

[0199] Then, -alignment films 110 and 230 are formed on the TFTsubstrate 100 and the opposed substrate 200, respectively (see FIGS. 19and 20E). The alignment films 110 and 230 are vertical alignment typepolyimide films. The thickness of the alignment films 110 and 230 may beset at about 60-100 nm.

[0200] Specifically, after the TFT substrate 100 and the opposedsubstrate 200 are cleaned, they are coated with respectivepolyimide-type vertical alignment films by one of spin coating,flexography, and screen printing. In this embodiment, polyimide filmsare applied by spin coating. Then, the polyimide films are cured byperforming preliminary baking at 80° C. for 5 minutes and thenperforming main baking by feeding a hot wind of 180° C. The alignmentfilms 110 and 230 are thus formed at a thickness of 80 nm.

[0201] In FIG. 20E, the alignment film 230 is drawn so as not to coverthe side faces and the top faces of the gap retaining members 220. Inthis embodiment, since the polyimide film is formed by spin coating,there may occur a case that the polyimide film covers the side faces andthe top faces of part of the gap retaining members 220. Since thepolyimide film (thickness: tens to hundreds of nanometers) is muchthinner than the gap retaining members 220 (height: several micrometers)and it may not assume a complete film on vertical surfaces such as theside faces of the gap retaining members 220, in FIG. 20E the alignmentfilm 230 is shown so as to be formed on only the horizontal surface.

[0202] Although in this embodiment the alignment films 110 and 230 aremade of polyimide, other resins such as acrylic, polyamide, andpolyimideamide may also be used. Further, they may be made of athermosetting resin.

[0203] Then, rubbing is performed in which each of the surface of thealignment film 110 on the TFT substrate 100 and the surface of thealignment film 230 on the opposed substrate 200 is rubbed in onedirection with a buff cloth (fiber of rayon, nylon, or the like) havinghair lengths of 2-3 mm. A TN mode alignment operation is performed inwhich the rubbing directions for the TFT substrate 100 and the opposedsubstrate 200 are perpendicular to each other.

[0204] In rubbing the TFT substrate 100, electrostatic breakdown of theTFTs formed in the TFT substrate 100 is prevented by preventinggeneration of static electricity by using an ion blow apparatus or ahumidifier.

[0205] On the other hand, in rubbing the opposed substrate 200, the kindand the hair planting density of the buff cloth and the rubbingconditions such as the roller rotation speed are selected or set so asnot to destroy the gal retaining members 220.

[0206] Then, an ultraviolet curable resin as a sealing agent 205 isapplied to a peripheral portion of the opposed substrate 200 so as toleave a liquid crystal injection inlet 206 (see FIG. 21A). Subsequently,the TFT substrate 100 and the opposed substrate 200 are opposed to eachother and then pressed against each other so that the cell gap in thepixel area 102 comes equal to the height of the gap retaining members220. The sealing agent 205 is cured in this state. The sealing agent 205may be applied to the TFT substrate 100 side.

[0207] Then, a liquid crystal material 300 as a display medium isinjected through the liquid crystal injection inlet 206, whereby theliquid crystal material is held between the TFT substrate 100 and theopposed substrate 200. After a sealing agent is applied to the liquidcrystal injection inlet 206, the sealing agent is cured by illuminatingit with ultraviolet light. The liquid crystal material 300 is thuscompletely sealed in the cell.

[0208] The configuration of FIG. 18 is obtained by the above steps.

[0209] Although in this embodiment the gap retaining members 220 areshaped like a cylinder, they may be shaped like an ellipse, astreamlined shape, or a polygon such as a triangle or a rectangle. Thegap retaining members 220 may have any shape as long as they can controlthe gap between the TFT substrate (first substrate) 100 and the opposedsubstrate (second substrate) 200.

[0210] Although this embodiment is directed to the reflection-typeliquid crystal display device in which the pixel electrodes are made ofa metal material, a transmission-type liquid crystal display device mayalso be configured because the TN mode type alignment operation isperformed. In such a case, the pixel electrodes may be transparentconductive films of ITO, SnO₂, or the like. Further, although thisembodiment is of the TN mode type, other modes may also be employed; therubbing may be performed in accordance with the mode.

[0211] Although this embodiment is directed to the case of using planarTFTs, naturally the invention is not limited by the TFT structure.Therefore, each TFT in the pixel area 102 and the driver circuit areas103 and 104 may be an inverted staggered structure TFT or a multi-gateTFT. Further, this embodiment can be applied to an IPS-type liquidcrystal panel in which also the opposed electrode is formed on the TFTsubstrate.

[0212] In this embodiment, since the gap retaining members 220 are madeof a photosensitive resin material, their height can be set as desired,for instance, at less than 2 μm. Therefore, the cell gap of the liquidcrystal display device can be made less than 2 μm. Therefore, the gapretaining members 220 of this embodiment are suitable for use in aliquid crystal panel of a ferroelectric liquid crystal display device orthat of a projection-type liquid crystal display device.

[0213] Further, in this embodiment, since the gap retaining members 220are fixed to the opposed substrate 200, they are not gathered due to theflow of a liquid crystal, unlike the conventional spacers. Therefore,point defects due to gathering of spacers can be prevented.

Embodiment 11

[0214] Although in the tenth embodiment rubbing is performed on both ofthe TFT substrate 100 side and the opposed substrate 200 side. In thisembodiment, rubbing is performed on only the alignment film 110 formedon the TFT substrate 100. The other part of the manufacturing process ofthis embodiment is the same as in the tenth embodiment.

[0215] Since a buff cloth that is used in the rubbing step is a sourceof static electricity and dust, the yield of the liquid crystal displaydevice strongly depends on the rubbing step. In this embodiment, toreduce the number of rubbing operations, rubbing is performed on onlythe TFT substrate 100 side.

[0216] As for the opposed substrate 200, the height of the gap retainingmembers 220 is several micrometers and the thickness of the alignmentfilm 230 is tens to hundreds of nanometers, and hence the gap retainingmembers 220 project to the liquid crystal side. Therefore, there is apossibility that the rubbing with the buff cloth damages or peels thegap retaining members 220. In such a case, the thickness of the gapretaining members 220 vary, making it difficult to keep the cell gapuniform over the entire substrate or among substrates. Further, damagedor peeled gap retaining members 220 become a new source of dust.

[0217] Further, since the gap retaining members 220 project to theliquid crystal side, it is difficult to form grooves in the alignmentfilm 230 in the intended manner, leaving a possibility that the liquidcrystal 300 will not be given proper alignment. Since display cannot beperformed if the liquid crystal 300 is not oriented properly, properlyorienting the liquid crystal 300 is an important factor in increasingthe production yield.

[0218] To avoid the above problems, in this embodiment, rubbing isperformed on only the alignment film 110 formed on the TFT substrate100.

[0219] In this embodiment, as in the tenth embodiment, the alignmentfilms 110 and 230 are vertical alignment type polyimide films. Rubbingis performed in such a manner that the surface of alignment film 110formed on the TFT substrate 100 is rubbed in a predetermined directionwith a buff cloth (fiber of rayon, nylon, or the like) having hairlengths of 2-3 mm. To prevent a reduction in the production yield of theTFT substrate 100, it is important that a proper measure be taken toprevent generation of static electricity in the step of rubbing the TFTsubstrate 100.

Embodiment 12

[0220] While in the eleventh embodiment rubbing is performed on only theTFT substrate 100 side, in this embodiment rubbing is performed on onlythe alignment film 230 formed on the opposed substrate 200. The otherpart of the manufacturing process of this embodiment is the same as inthe tenth embodiment (see FIG. 18).

[0221] Since a buff cloth that is used in the rubbing step is a sourceof static electricity and dust, the yield of the liquid crystal displaydevice strongly depends on the rubbing step. In this embodiment, toreduce the number of rubbing operations, rubbing is performed on onlythe opposed substrate 200 side.

[0222] The buff cloth used in the rubbing step causes static electricityand dust, which may destroy the TFTs that are formed in the TFTsubstrate 100. More steps are needed to produce the TFT substrate 100than to produce the opposed substrate 200. Therefore, frequentoccurrence of defects in TFT substrates 100 increases the manufacturingcost of the liquid crystal display device. This embodiment is intendedto increase the production yield of the TFT substrate 100 by refrainingfrom rubbing the TFT substrate 100 side.

[0223] In this embodiment, as in the tenth embodiment, the alignmentfilms 110 and 230 are vertical alignment type polyimide films. Rubbingis performed in such a manner that the surface of alignment film 230formed on the opposed substrate 200 is rubbed in a predetermineddirection with a buff cloth (fiber of rayon, nylon, or the like) havinghair lengths of 2-3 mm. The rubbing conditions are set so as not todamage or peel the gap retaining members 220 formed on the opposedsubstrate 200.

[0224] Although the eleventh and twelfth embodiments are the same inthat rubbing is performed on only one substrate side, they havedifferent effects. A party who practice the invention may select asubstrate to be subjected to rubbing in consideration of themanufacturing cost, the yield, and other factors.

[0225] Where rubbing is performed on only one of the alignment films asin the case of the eleventh and twelfth embodiments, available liquidcrystal driving modes are restricted. However, the inventors haveconfirmed that the birefringence (ECB) mode is available.

[0226] On the other hand, where rubbing is performed on both alignmentfilms as in the case of the tenth embodiment, there are advantages thatavailable liquid crystal driving modes are not restricted and the liquidcrystal can be oriented reliably though rubbing operations need to beperformed one time more than in the eleventh and twelfth embodiments.Where the invention is applied to a polymer dispersion type liquidcrystal display device, no alignment film rubbing operation isnecessary.

Embodiment 13

[0227] This embodiment is directed to modification to the arrangement ofthe gap retaining members and is the same as the tenth embodiment in theother points. FIG. 22 is a top view of an opposed substrate according tothis embodiment. The members in FIG. 22 that are given the samereference numerals as in FIGS. 21A and 21B are the same as thecorresponding members in FIGS. 21A and 21B.

[0228] In the tenth embodiment, the gap retaining members 220 arearranged randomly on the entire opposed substrate 200 as shown in FIG.21A. In contrast, in this embodiment, as shown in FIG. 22, gap retainingmembers 700 are arranged regularly in matrix form. The shape of the gapretaining members 700 are the same as in the tenth embodiment, that is,they are shaped like a cylinder of 2.0 μm in diameter and 3.2 μm inheight. Also as in the case of the tenth embodiment, the gap retainingmembers 700 are arranged at a density of 50 mm⁻².

[0229] The gap retaining members 700 of this embodiment provides thesame advantages as the gap retaining members 220 of the tenthembodiment.

Embodiment 14

[0230] This embodiment is directed to modification to the arrangement ofthe gap retaining members and is the same as the tenth embodiment in theother points. FIG. 23 is a top view of an opposed substrate according tothis embodiment. The members in FIG. 23 that are given the samereference numerals as in FIGS. 21A and 21B are the same as thecorresponding members in FIGS. 21A and 21B.

[0231] In the tenth embodiment, the gap retaining members 220 arearranged randomly on the entire opposed substrate 200 as shown in FIGS.21A. In contrast, in this embodiment, as shown in FIG. 23, gap retainingmembers 710 are arranged randomly in the pixel-confronting area 202 soas not to be formed in the driver-circuit-confronting areas 203 and 204.The shape of the gap retaining members 710 are the same as in the tenthembodiment, that is, they are shaped like a cylinder of 2.0 μm indiameter and 3.2 μm in height. The gap retaining members 710 arearranged at a density of 60 mm⁻².

[0232] Since the TFTs in the driver circuit areas 103 and 104 have ahigher integration density than the TFTs in the pixel area 102, they areprone to be broken by stress that is imposed by the spacers. In thisembodiment, since no gap retaining members 710 are formed in thedriver-circuit-confronting areas 203 and 204, when the TFT substrate 100and the opposed substrate 200 are bonded together the gap retainingmembers 710 do not exert stress on the driver circuits formed in the TFTsubstrate 100. Therefore, the yield of the driver circuits can beincreased.

[0233] In FIG. 23, there are gap retaining members 710 that partiallyexist outside the pixel-confronting area 202. This embodiment onlyrequires that the gap retaining members 710 can retain the gap in thepixel area 202, and that the gap retaining members 710 not be formed inthe driver-circuit-confronting areas 203 and 204.

[0234] In the tenth and thirteenth embodiments, the gap retainingmembers 220 are formed in the pixel-confronting area 202 anddisclination is prone to occur around the gap retaining members 220.Therefore, where the gap retaining members 220 are formed in thepixel-confronting area 202, to prevent display defects, it is preferablethat the gap retaining members 220 be formed in regions that do notcontribute to the display, for instance, regions where a black matrix orbus lines of the TFT substrate 100 are formed.

Embodiment 15

[0235] This embodiment is directed to modification to the arrangement ofthe gap retaining members and is the same as the tenth embodiment in theother points. FIGS. 24A and 24B are top views of opposed substratesaccording to this embodiment. The members in FIGS. 24A and 24B that aregiven the same reference numerals as in FIGS. 21A and 21B are the sameas the corresponding members in FIGS. 21A and 21B.

[0236] While in the fourteenth embodiment the gap retaining members 710are not formed in the driver-circuit-confronting areas 203 and 204, inthis embodiment gap retaining members are not formed in thedriver-circuit-confronting areas 203 and 204 nor the pixel-confrontingarea 202.

[0237] There are a height difference between the pixel-confronting area202 and the driver-circuit-confronting areas 203 and 204; in general,the height is greater in the pixel-confronting area 202. However, in thetenth embodiment, the height of the gap retaining members 220 from thesubstrate 201 to their top faces is made uniform over the entire opposedsubstrate 200. Therefore, as the height difference between thepixel-confronting area 202 and the driver-circuit-confronting areas 203and 204 increases, it becomes more difficult to compensate for theheight difference and a cell gap variation becomes more prone to occurin bonding the substrates 100 and 200 together.

[0238] In the tenth and thirteenth embodiments, since the gap retainingmembers 220 or 700 are formed on the entire opposed substrate 200, thereis a possibility that gap retaining members 220 or 700 damage the TFTsthat are formed in the pixel area 202 and the driver circuit areas 103and 104.

[0239] This embodiment is directed to a method of forming gap retainingmembers that solves the above problems, that is, prevents a cell gapvariation as well as prevents the TFTs that are formed in the TFTsubstrate 100 from being damaged.

[0240]FIGS. 24A and 24B are top views of opposed substrates 200according to this embodiment. The opposed substrates 200 are produced inthe same manner as in the tenth embodiment.

[0241] In this embodiment, as shown in FIG. 24A, cylindrical gapretaining members 720 are arranged so as to surround thepixel-confronting area 202. Specifically, the gap retaining members 720are shaped like a cylinder of 10 μm in diameter and 3.2 μm in height.The gap retaining members 720 are located so as to be separated by 70 μmfrom the end of the pixel area 102 of the TFT substrate 100 in the statethat the substrates 100 and 200 are bonded together. The intervalbetween the gap retaining members 720 are set at 30 μm. The arrangementdensity of the gap retaining members 720 in the vicinity of a liquidcrystal injection inlet 206 is made lower than in the other portions tofacilitate the flow of a liquid crystal.

[0242] The intervals between the pixel-confronting area 202 and thedriver-circuit-confronting areas 203 and 204 are hundreds ofmicrometers, which is sufficiently longer than the diameter of the gapretaining members 720. Therefore, the manufacturing margin of thepositions of the gap retaining members 720 is as large as about ±10 μm.On the other hand, the accuracy of the height of the gap retainingmembers 720 is an important factor in determining the cell gap, and isset at about ±0.1 μm in this embodiment.

[0243] While in FIG. 24A the gap retaining members 720 are formed onlyaround the pixel-confronting area 202, gap retaining members 721 and 722may additionally be formed around the driver-circuit-confronting areas203 and 204 as shown in FIG. 24B.

[0244] In this embodiment, the gap retaining members 720 are formed inthe regions that do not overlap with the pixel area 102 nor the drivercircuit areas 103 and 104 when the substrates 100 and 200 are bondedtogether. Therefore, the cell gap is determined by only the height ofthe gap retaining members 720 (and 721 and 722). Therefore, even ifthere is a height difference between the pixel area 102 and the drivercircuit areas 103 and 104, the cell gas can be made uniform over theentire substrate or among different substrates.

[0245] Further, since the gap retaining members 720 do not press thepixel TFTs nor the driver circuit TFTs formed in the TFT substrate 100,the yield can be increased.

[0246] Although in this embodiment the gap retaining members 720 (and721 and 722) are formed around the pixel-confronting area 202 (and thedriver-circuit-confronting areas 203 and 204), the positions of the gapretaining members are not limited to those shown in FIGS. 24A and 24B.The gap retaining members may be formed anywhere except thepixel-confronting area 202 and the driver-circuit-confronting areas 203and 204 as long as they can retain the cell gap.

Embodiment 16

[0247] This embodiment is a modification of the fifteenth embodiment.FIGS. 25A and 25B are a top view and an enlarged perspective view,respectively, of an opposed substrate according to this embodiment. Themanufacturing method of the opposed substrate is the same as in thetenth embodiment, and members in FIGS. 25A and 25B that are given thesame reference numerals as in FIGS. 21A and 21B are the same as thecorresponding members in FIGS. 21A and 21B.

[0248] In this embodiment, a gap retaining member 730 is approximatelyshaped like a wall that erects from the substrate 201. The gap retainingmember 730 surrounds a pixel-confronting area 202 and is connected tothe liquid crystal injection inlet 206. The gap retaining member 730 is20 μm in width and 3.2 μm in height and is separated from the end of thepixel-confronting area 202 by 50 μm.

[0249] In this embodiment, the gap retaining member 730 is formed in anarea that does not overlap with any of the pixel area 102 and the drivercircuit areas 103 and 104 when the substrates 100 and 200 are bondedtogether. Since the cell gap is determined by only the height of the gapretaining member 730, the cell gap can be made uniform over the entiresubstrate or among different substrates even if there is a heightdifference between the pixel area 102 and the driver circuit areas 103and 104.

[0250] Since the gap retaining member 730 does not press the TFTs formedin the TFT substrate 100, the yield can be increased.

[0251] Further, as shown in FIG. 26, this embodiment has a feature thatthe gap retaining member 730 has a structure that enables sealing of aliquid crystal in the pixel area 102. Because of the presence of the gapretaining member 730, a liquid crystal is injected into only the spacecorresponding to the pixel area 102 and is not injected into the spacescorresponding to the driver circuit areas 103 and 104. Therefore, theload capacitances of the driver circuits can be reduced and hencecrosstalk can be made less prone to occur.

[0252] While in FIG. 25A the gap retaining member 730 is formed onlyaround the pixel-confronting area 202, as shown in FIG. 26 wall-shapedgap retaining members 731 and 732 similar to the gap retaining member730 may additionally be formed around the driver-circuit-confrontingareas 203 and 204.

[0253] In this embodiment, it is sufficient that the gap retainingmember 730 has a structure that enables sealing of a liquid crystal inthe pixel area 102, and hence the shape of the gap retaining members 731and 732 is not limited to the wall-like shape and may be a cylindricalshape, an elliptical pole shape, a rectangular prism shape, or apolygonal prism shape. The positions of the gap retaining members 731and 732 are not limited to the neighborhood of thedriver-circuit-confronting areas 203 and 204; they may be formedanywhere except the pixel-confronting area 202 and theperipheral-circuit-confronting areas 203 and 204 as long as they canretain the cell gap.

Embodiment 17

[0254] This embodiment is a modification of the sixteenth embodiment.This embodiment has a feature that gap retaining members are configuredso that a liquid crystal is injected into the space corresponding to thepixel area 102 but is not injected into the spaces corresponding to thedriver circuit areas 103 and 104. FIG. 27 is a top view of an opposedsubstrate according to this embodiment. The manufacturing method of theopposed substrate is the same as in the tenth embodiment, and members inFIG. 27 that are given the same reference numerals as in FIGS. 21A and21B are the same as the corresponding members in FIGS. 21A and 21B.

[0255] In this embodiment, as shown in FIG. 27, thedriver-circuit-confronting areas 203 and 204 are surrounded by awall-shaped gap retaining member 741 so that a liquid crystal 300 doesnot enter the driver circuit areas 103 and 104 in the state that thesubstrates 100 and 200 are bonded together.

[0256] In this embodiment, as shown in FIG. 27, the gap retaining member714 is approximately shaped like a wall that erects from the substrate201. The gap retaining member 714 is 20 μm in width and 3.2 μm in heightand is separated from the end of the driver-circuit-confronting areas203 and 204 by 50 μm.

[0257] In this embodiment, rectangular-prism-like gap retaining member740 are arranged so as to surround the pixel-confronting area 202 sothat a liquid crystal can flow into the pixel area 102. Each gapretaining member 740 is shaped like a rectangular prism in which thelong side length is 30 μm, the short side length is 15 μm, and theheight is 3.2 μm. The gap retaining members 740 are separated from theend of the pixel-confronting area 202 by 70 μm, and the interval betweenadjacent ones of the gap retaining members 740 is set at 30 μm. Thearrangement density of part of the gap retaining members 740 in thevicinity of the liquid crystal injection inlet 206 is made lower than inthe other portions to facilitate injection of a liquid crystal.

[0258] Although the tenth to seventeenth embodiments are directed to thecase where a liquid crystal material is used as a display medium, theinvention can also be applied to a case of using a mixed layer of aliquid crystal and a polymer, that is, the invention can also be appliedto a polymer dispersion type liquid crystal display device.

Embodiment 18

[0259] This embodiment is directed to a case where the invention isapplied to an STN reflection type liquid crystal panel. FIG. 28 is aschematic perspective view of a liquid crystal panel according to thisembodiment. As shown in FIG. 28, striped reflective electrodes 1110, analignment film 1120, and gap retaining members 1300 are provided on aglass substrate 1000. To retain the cell gap, the gap retaining members1300 are arranged uniformly over the entire substrate 1000. On the otherhand, transparent electrodes 1210 and an alignment film 1220 areprovided on a glass substrate 1200. The glass substrates 1000 and 1200are opposed to each other with the alignment films 1120 and 1220 locatedinside. The interval between the glass substrates 1000 and 1200 issecured by the gap retaining members 1300, and an STN liquid crystal issealed in the space between the substrates 1000 and 1200.

[0260] A manufacturing method of the reflection-type liquid crystalpanel according to this embodiment will be described with reference toFIGS. 29A-29F to 31. First, to form reflective electrodes 1110, a metalfilm is formed on a glass substrate 1000. In this embodiment, a400-nm-thick aluminum film is formed by sputtering and then patternedinto striped reflective electrodes 1110 (see FIG. 29A). The reflectiveelectrodes 1110 extend in the direction perpendicular to the papersurface of FIGS. 29A-29F.

[0261] Then, to form gap retaining members 1130, a coating 910 is formedby using an insulative material. In this embodiment, a 3.5-μm-thickphotosensitive polyimide film 910 is formed by spin coating and thenleft at the room temperature for 30 minutes (leveling) to uniformize thethickness of the photosensitive polyimide film 910 over the TFTsubstrate. Thereafter, the glass substrate 1000 on which thephotosensitive polyimide film 910 is formed is pre-baked at 120° C. for3 minutes (see FIG. 29B).

[0262] Then, the top surface of the photosensitive polyimide film 910 isplanarized by chemical mechanical polishing (CMP). In this embodiment,slurry that is used in the CMP step is a colloid-like one in which asilica (SiO₂) fine powder is dispersed in an acid solution. As for theCMP conditions, each of the substrate and an abrasive cloth is rotatedat 50 rpm and the polishing time is set at 3 minutes. In this CMP step,the top 1-μm layer of the photosensitive polyimide film 910 is removedby polishing, whereby a polished photosensitive polyimide film 920 has aheight of 2.6 μm as measured from the surfaces of the reflectiveelectrodes 1110.

[0263] Although in this embodiment the slurry that is used in the CMPstep is one in which a silica fine powder is dispersed in an acidsolution, slurry obtained by dispersing aluminum oxide (Al₂O₃), ceriumoxide (CeO₂), or the like in an acid solution may also be used. It isdesirable that the slurry be changed in accordance with the materialthat is subjected to CMP. Further, the optimum rotation speed of each ofthe substrate and an abrasive cloth and processing time may bedetermined in accordance with a material to be subjected to CMP and thepolishing removal thickness.

[0264] The cell gap (interval between the substrates) is determined bythe thickness of the photosensitive polyimide film 920 that has beenobtained by CMP. Therefore, the thickness of the photosensitivepolyimide film 910 before being subjected to CMP may be set properly inaccordance with the desired cell gap and the polishing removalthickness.

[0265] Even if the thickness of the photosensitive polyimide film 910before being subjected to CMP varies from one substrate to another, thethickness of the photosensitive polyimide film 920 can be made uniformamong different substrates by adjusting the polishing removal thickness.

[0266] Then, to pattern the photosensitive polyimide film 920 that hasbeen obtained by CMP, the photosensitive polyimide film 920 is coveredwith a photomask 930 as shown in FIG. 29D. Although in FIG. 29D thephotomask 930 is drawn as if it were divided, actually it is an integrallayer having circular openings.

[0267] Ultraviolet light is applied in the state of FIG. 29D.Subsequently, development is performed and then post-baking is performedat 280° C. for one hour. In this manner, as shown in FIG. 29E, portionsof the photosensitive polyimide film 920 that have been illuminated withultraviolet light remain and cylindrical gap retaining members 1300 areformed.

[0268] Then, a polyimide-type vertical alignment film 1120 is formed onthe substrate 1000 by one of spin coating, flexography, and screenprinting. In this embodiment, to reduce physical impact on the gapretaining members 1300, the alignment film 1120 is formed by spincoating. Thereafter, the polyimide film 1120 is cured by baking it byfeeding a hot wind of 180° C. Settings are made so that after the curingthe alignment film has a thickness of 100 nm (see FIG. 29F).

[0269]FIG. 32 is a top view of the substrate 100 in the state of FIG.29F. In this embodiment, the gap retaining members 1300 are shaped likea cylinder with a circular cross-section in which the bottom facediameter is 3 μm and the height as measured from the surface of thealignment film 1120 is about 2.5 μm. The gap retaining members 1300 arearranged regularly at a density of 50 mm⁻². The arrangement density ofthe gap retaining members 1300 may be set at 40-160 mm⁻², which isapproximately equal to the dispersion density of conventional spacers,in accordance with the strength of the gap retaining members 1300.

[0270] In this embodiment, the gap retaining members 1300 are formed atpositions on the reflective electrodes 1110 where the top faces 1300 aof the respective gap retaining members 1300 confront the transparentelectrodes 1210 in the state that the glass substrates 1000 and 1200 areopposed to each other.

[0271] The surface (to contact a liquid crystal material) of each glasssubstrate 1000 or 1200 has periodic asperities due to the multilayeredstructure including the striped electrodes 1110 or 1210. In the statethat the glass substrates 1000 and 1200 are opposed to each other, thecell gap varies periodically due to those asperities. In view of this,in this embodiment, all the gap retaining members 1300 are formed atpositions having almost the same cell gap value and the heights of therespective gap retaining members 1300 are approximately equalized byCMP. In this manner, the cell gap is made uniform over the entiresubstrate.

[0272] In FIG. 29F, the alignment film 1120 is drawn so as not to coverthe side faces and the top faces 1300 a of the gap retaining members1300. This is because in this embodiment the alignment film 1120 may notassume a complete film on the side faces and the top faces 1300 a of thegap retaining members 1300 that are erected as shown in FIG. 29F,because the polyimide film is formed by spin coating and the polyimidefilm (thickness: tens to hundreds of nanometers) is much thinner thanthe gap retaining members 1300 (height: several micrometers). Thus, FIG.29F shows only the alignment film 1120 that is formed on the horizontalsurface and assumes a complete film.

[0273] Next, a process to be executed on the glass substrate 1200 willbe described with reference to FIGS. 30A and 30B. Color filters 1230 areformed on the glass substrate 1200, and then a protective film 1240 madeof an acrylic resin or an epoxy resin is formed on the color filters1230. In this embodiment, a 1-μm-thick acrylic resin is formed as theprotective film 1240 (see FIG. 30A). In FIG. 28, the color filters 1230and the protective film 1240 are omitted.

[0274] Then, transparent conductive films of ITO (indium tin oxide),SnO₂ (tin oxide), or the like are formed as transparent electrodes 1210.In this embodiment, an ITO film is formed by sputtering and thenpatterned into striped transparent electrodes 1210. Thereafter, apolyimide-type vertical alignment film 1220 is formed by the same methodas the alignment film 1120 is formed (see FIG. 30B).

[0275] Then, rubbing is performed on each of the alignment films 1120and 1220. In this embodiment, each of the alignment films 1120 and 1220is rubbed with a roller on which a buff cloth (fiber of rayon or nylon)having hair lengths of 2-3 mm is wound. The rubbing direction is setparallel with one of the diagonals of the glass substrate 1000 or 1200.The directions of rubbing on the alignment films 1120 and 1220 are setso as to be perpendicular to each other in the state that the glasssubstrates 1000 and 1200 are opposed to each other.

[0276] As for the glass substrate 1000, the gap retaining members 1300project from the alignment film 1120. Therefore, there is a possibilitythat the gap retaining members 1300 are damaged or peeled. This problemcan be avoided by properly adjusting the kind and the hair plantingdensity of a buff cloth, the rotation speed of the roller, the number ofrubbing operations, and other factors.

[0277] Then, a sealing agent for bonding the glass substrates 1000 and1200 together is applied to one of the glass substrates 1000 and 1200.In this embodiment, a sealing agent made of an ultraviolet curable resinis applied to a peripheral portion of the glass substrate 1200 so as toleave a liquid crystal injection inlet. Thereafter, the glass substrates1000 and 1200 are opposed to each other and pressed against each otherso that the cell gap becomes equal to the height of the gap retainingmembers 1300. The sealing agent is cured in this state by illuminatingit with ultraviolet light.

[0278] Then, a liquid crystal is injected through the liquid crystalinjection inlet. Subsequently, a sealing agent is applied to the liquidcrystal injection inlet and then cured by illuminating it withultraviolet light. The liquid crystal is thus completely sealed in thecell. Then, a phase plate 1510, a polarizer 1520, and a forwardscattering plate 1530 are provided on the back surface of the glasssubstrate 1200. As a result of the execution of the above steps, afull-color STN liquid crystal panel shown in FIG. 31 is completed.

[0279]FIG. 31 is a sectional view of the liquid crystal panel. In FIG.31, the striped reflective electrodes 1110 extend in the directionparallel with the paper surface and the striped transparent electrodes1210 extend in the direction perpendicular to the paper surface

[0280] In this embodiment, the reason why the gap retaining members 1300are provided on the glass substrate 1000 side is that the color filters1230 are provided on the glass substrate 1200 side. The gap retainingmembers 1300 are formed through chemical mechanical polishing, whichinvolves application of physical force. In this embodiment, to minimizethe rate of occurrence of defective products, the gap retaining members1300 are provided on the glass substrate 1000 side where the colorfilters 1230 are not provided.

[0281] This embodiment is directed to the full-color panel. On the otherhand, the color filters 1230 are not required in black-and-white displaypanels, three-panel-type projection display panels, etc. In such cases,the gap retaining members 1300 may be provided on either the glasssubstrate 1000 or 1200. That is, the substrate to be provided with thegap retaining members 1300 may be selected so that the rate ofoccurrence of defective products is reduced in the manufacturingprocess.

[0282] Although this embodiment is directed to the reflection-typeliquid crystal panel, the gap retaining members 1300 of this embodimentcan be used in transmission-type panels.

[0283] Although in this embodiment the gap retaining members 1300 arearranged regularly, they may be arranged randomly, for example, as shownin FIG. 33. Even in such a case the gap retaining members 1300 are notgathered at a single location unlike the conventional spacers, becausetheir positions are determined by the photomask 930.

[0284] Although in this embodiment the bottom face of each gap retainingmember 1300 is a circle, it may be an ellipse or may have a streamlinedshape or a polygonal shape such as a triangle or a rectangle. The gapretaining members 1300 may assume any shape as long as they can controlthe cell gap and provide sufficient strength. Although in thisembodiment all the gap retaining members 1300 have the same shape, gapretaining members 1300 having plural kinds of shapes may be formed onthe same substrate. In this embodiment, since the shape of the bottomface of each gap retaining member 1300 is determined by the photomask930, it can be changed easily with high accuracy.

[0285] Although in this embodiment the arrangement density of the gapretaining members 1300 is set uniform, it may be increased in aparticular region, for instance, to increase the strength there. In thisembodiment, since the arrangement density of each gap retaining memberis determined by the photomask 930, it can be changed easily with highaccuracy.

Embodiment 19

[0286] While the eighteenth embodiment is directed to the STN liquidcrystal panel, the invention can be applied to a liquid crystal panelusing a ferroelectric liquid crystal. In this embodiment, in thereflection-type panel shown in FIG. 28, the gap retaining members 1300are formed so as to assume a cylinder in which the height as measuredfrom the reflective electrodes 1110 is 1.5 μm and the bottom face is acircle of 2 μm in diameter. The manufacturing method, the positions offormation, and the arrangement density of the gap retaining members 1300are the same as in the eighteenth embodiment.

[0287] The cell gap can be determined as desired by the gap retainingmembers 1300 and their positions of formation can be controlled.Further, the faces confronting the other substrate is made flat.Therefore, by virtue of the use of the gap retaining members 1300, thecell gap that is smaller than the spiral pitch of a ferroelectric liquidcrystal can be made uniform with high accuracy over the entiresubstrate.

[0288] Ferroelectric liquid crystals have features that no crosstalkoccurs, the viewing angle is wide, and the switching speed is threeorders or more higher than that of STN liquid crystals, and hence canrealize high-resolution, large-screen displays even with the passivematrix driving scheme. Therefore, the use of the gap retaining members1300 of this embodiment makes it possible to provide, at a low cost, ahigh-resolution, large-screen ferroelectric liquid crystal panel.

[0289] Further, an antiferroelectric liquid crystal can be used insteadof a ferroelectric liquid crystal. Also in the case of using anantiferroelectric liquid crystal, the cell gap needs to be made lessthan 2 μm so that the spiral structure of the liquid crystal disappear.By using the gap retaining members 1300 of this embodiment, the cell gapcan be made less than 1.5 μm.

[0290] As described above, according to the invention, a semiconductordisplay device having a uniform cell thickness profile can be obtained.Further, according to the invention, since a desired cell gap can besecured without scattering grainy spacers, there can be prevented anevent that unnecessary force is exerted on the driver circuit TFTs inbonding the substrates together, which leads to an increase in the yieldof products.

[0291] According to another aspect of the invention, the accuracy of thecell gap can be made high because the top faces of the gap retainingmembers are planarized and the planarization is performed by chemicalmechanical polishing. This makes it possible to provide anelectro-optical device having a uniform cell thickness profile. Further,according to this aspect of the invention, since a desired cell gap canbe secured without scattering grainy spacers, there can be prevented anevent that unnecessary force is exerted on the driver circuit TFTs inbonding the substrates together, which leads to an increase in the yieldof products.

[0292] According to a further aspect of the invention, since the gapretaining members are provided on the opposed substrate, influences(etchant-related influences, mechanical impact, etc.) of the formationof the gap retaining members do not affect the elements formed in theTFT substrate, which leads to an increase in yield.

[0293] Further, providing the gap retaining members on the opposedsubstrate makes it easier to select a material of the gap retainingmembers than providing those on the TFT substrates in which theswitching elements such as TFT is are provided. Further, by providingthe gap retaining members on the opposed substrate, materials such as anetchant and means that are necessary to form the gap retaining memberscan be selected from wider ranges.

What is claimed is:
 1. A method of manufacturing a display devicecomprising: forming a switching element adjacent to a first substrate;forming a pixel electrode electrically connected to the switchingelement; forming a gap retaining member adjacent to a second substrateby patterning; forming a vertical alignment film adjacent to the secondsubstrate; disposing a liquid crystal layer between the first substrateand the second substrate.
 2. A method of manufacturing a display devicecomprising: forming a switching element adjacent to a first substrate;forming a pixel electrode electrically connected to the switchingelement; forming a second electrode adjacent to a second substrate;forming a gap retaining member adjacent to the second electrode bypatterning; forming a vertical alignment film adjacent to the secondsubstrate; disposing a liquid crystal layer between the first substrateand the second substrate.
 3. A method of manufacturing a display devicecomprising: forming a switching element adjacent to a first substrate;forming a pixel electrode electrically connected to the switchingelement; forming a second electrode adjacent to a second substrate;forming a gap retaining member adjacent to the second electrode bypatterning; forming a vertical alignment film adjacent to the secondsubstrate; disposing a liquid crystal layer between the first substrateand the second substrate, wherein said vertical alignment film is nottreated with a rubbing treatment.
 4. A method of manufacturing a displaydevice comprising: forming a switching element adjacent to a firstsubstrate; forming a pixel electrode electrically connected to theswitching element; forming a gap retaining member adjacent to a secondsubstrate by patterning; forming an alignment film adjacent to thesecond substrate; disposing a liquid crystal layer between the firstsubstrate and the second substrate, wherein said display device is anECB mode device.
 5. A method of manufacturing a display devicecomprising: forming a switching element adjacent to a first substrate;forming a pixel electrode electrically connected to the switchingelement; forming a second electrode adjacent to a second substrate;forming a gap retaining member adjacent to the second electrode bypatterning; forming an alignment film adjacent to the second substrate;disposing a liquid crystal layer between the first substrate and thesecond substrate, wherein said display device is an ECB mode device. 6.A method of manufacturing a display device comprising: forming aswitching element adjacent to a first substrate; forming a pixelelectrode electrically connected to the switching element; forming asecond electrode adjacent to a second substrate; forming a gap retainingmember adjacent to the second electrode by patterning; forming analignment film adjacent to the second substrate; disposing a liquidcrystal layer between the first substrate and the second substrate,wherein said vertical alignment film is not treated with a rubbingtreatment, and wherein said display device is an ECB mode device.
 7. Amethod of manufacturing a display device comprising: forming a switchingelement adjacent to a first substrate; forming a pixel electrodeelectrically connected to the switching element; forming a gap retainingmember adjacent to a second substrate by patterning; forming a verticalalignment film adjacent to the second substrate; disposing a liquidcrystal layer between the first substrate and the second substrate,wherein said display device is an ECB mode device.
 8. A method ofmanufacturing a display device comprising: forming a switching elementadjacent to a first substrate; forming a pixel electrode electricallyconnected to the switching element; forming a second electrode adjacentto a second substrate; forming a gap retaining member adjacent to thesecond electrode by patterning; forming a vertical alignment filmadjacent to the second substrate; disposing a liquid crystal layerbetween the first substrate and the second substrate, wherein saiddisplay device is an ECB mode device.
 9. A method of a display devicecomprising: forming a switching element adjacent to a first substrate;forming a pixel electrode electrically connected to the switchingelement; forming a second electrode adjacent to a second substrate;forming a gap retaining member adjacent to the second electrode bypatterning; forming a vertical alignment film adjacent to the secondsubstrate; disposing a liquid crystal layer between the first substrateand the second substrate, wherein said vertical alignment film is nottreated with a rubbing treatment, and wherein said display device is anECB mode device.
 10. A method of manufacturing a display devicecomprising: forming a switching element adjacent to a first substrate;forming a pixel electrode electrically connected to the switchingelement; forming a gap retaining member adjacent to a second substrateby patterning; forming a vertical alignment film adjacent to the secondsubstrate after the formation of the gap retaining member; disposing aliquid crystal layer between the first substrate and the secondsubstrate.
 11. A method of manufacturing a display device comprising:forming a switching element adjacent to a first substrate; forming apixel electrode electrically connected to the switching element; forminga second electrode adjacent to a second substrate; forming a gapretaining member adjacent to the second electrode by patterning; forminga vertical alignment film adjacent to the second substrate after theformation of the gap retaining member; disposing a liquid crystal layerbetween the first substrate and the second substrate.
 12. A method ofmanufacturing a display device comprising: forming a switching elementadjacent to a first substrate; forming a pixel electrode electricallyconnected to the switching element; forming a second electrode adjacentto a second substrate; forming a gap retaining member adjacent to thesecond electrode by patterning; forming a vertical alignment filmadjacent to the second substrate after the formation of the gapretaining member; disposing a liquid crystal layer between the firstsubstrate and the second substrate, wherein said vertical alignment filmis not treated with a rubbing treatment.
 13. A method of manufacturing adisplay device comprising: forming a switching element adjacent to afirst substrate; forming a pixel electrode electrically connected to theswitching element; forming a gap retaining member adjacent to a secondsubstrate by patterning; forming an alignment film adjacent to thesecond substrate after the formation of the gap retaining member;disposing a liquid crystal layer between the first substrate and thesecond substrate, wherein said display device is an ECB mode device. 14.A method of manufacturing a display device comprising: forming aswitching element adjacent to a first substrate; forming a pixelelectrode electrically connected to the switching element; forming asecond electrode adjacent to a second substrate; forming a gap retainingmember adjacent to the second electrode by patterning; forming analignment film adjacent to the second substrate after the formation ofthe gap retaining member; disposing a liquid crystal layer between thefirst substrate and the second substrate, wherein said display device isan ECB mode device.
 15. A method of manufacturing a display devicecomprising: forming a switching element adjacent to a first substrate;forming a pixel electrode electrically connected to the switchingelement; forming a second electrode adjacent to a second substrate;forming a gap retaining member adjacent to the second electrode bypatterning; forming an alignment film adjacent to the second substrateafter the formation of the gap retaining member; disposing a liquidcrystal layer between the first substrate and the second substrate,wherein said vertical alignment film is not treated with a rubbingtreatment, and wherein said display device is an ECB mode device.
 16. Amethod of manufacturing a display device comprising: forming a switchingelement adjacent to a first substrate; forming a pixel electrodeelectrically connected to the switching element; forming a gap retainingmember adjacent to a second substrate by patterning; forming a verticalalignment film adjacent to the second substrate after the formation ofthe gap retaining member; disposing a liquid crystal layer between thefirst substrate and the second substrate, wherein said display device isan ECB mode device.
 17. A method of manufacturing a display devicecomprising: forming a switching element adjacent to a first substrate;forming a pixel electrode electrically connected to the switchingelement; forming a second electrode adjacent to a second substrate;forming a gap retaining member adjacent to the second electrode bypatterning; forming a vertical alignment film adjacent to the secondsubstrate after the formation of the gap retaining member; disposing aliquid crystal layer between the first substrate and the secondsubstrate, wherein said display device is an ECB mode device.
 18. Amethod of manufacturing a display device comprising: forming a switchingelement adjacent to a first substrate; forming a pixel electrodeelectrically connected to the switching element; forming a secondelectrode adjacent to a second substrate; forming a gap retaining memberadjacent to the second electrode by patterning; forming a verticalalignment film adjacent to the second substrate after the formation ofthe gap retaining member; disposing a liquid crystal layer between thefirst substrate and the second substrate, wherein said verticalalignment film is not treated with a rubbing treatment, and wherein saiddisplay device is an ECB mode device.
 19. The method according to anyone of claims 1 to 18 wherein said switching element comprises aninverted staggered thin film transistor.
 20. The method according to anyone of claims 1 to 18 wherein said gap retaining member comprises anultraviolet curable resin.
 21. The method according to any one of claims1 to 18 wherein said gap retaining member comprises a photocurablepolyimide.
 22. The method according to any one of claims 1 to 18 whereinsaid gap retaining member a thermosetting resin.
 23. The methodaccording to any one of claims 1 to 18 wherein said gap retaining memberhas a streamlined shape.
 24. The method according to any one of claims 1to 18 wherein said gap retaining member has an ellipse shape.
 25. Themethod according to any one of claims 1 to 18 wherein said gap retainingmember has a polygon shape.
 26. The method according to any one ofclaims 1 to 18 wherein said gap retaining member is 2.0-5.0 μm inheight.
 27. The method according to any one of claims 1 to 18 whereinsaid gap retaining member is formed at a density of 40-160/mm².